In our world's 2016, the German town of Munich is part of the country of Germany.
Now in an alternate Earth I would like Munich to be part of the Great French Empire (in the alternate year of 2016 naturally).
Q: What change in history could fabricate this situation? And why?
Answers will be rated on:
The thoroughness of the explanation
The less far back in time the change needs to happen1
1e.g. a change around WW2 will be rated higher than a change back in the time of the Empire of Francia
In 1930's England, two people are taken much more seriously than they were in our history - Basil Liddell-Hart and Frank Whittle. Liddell-Hart's concept of fully mechanised forces means that the BEF deployed to France is more than a match for the Wehrmacht and SS; whilst Whittle's jet engine gives the RAF a huge advantage over the Luftwaffe.
Meanwhile in France the the Maginot Line isn't over-relied upon, and the Allies stand ready to face the Germans wherever they attack.
The net result is that Germany suffers a humilating defeat in 1940; Poland is liberated and Germany is split between the victors. Britain and France are able - now without having to worry about fighting on two fronts - are able to keep Japan at bay and keep an uneasy peace.
Without Japan's entry into the war, the US remains neutral, and with Britain and France not worn down by years of war they are able to counter the US's interest in de-colonialism; the US protests their annexation of Germany but with the memory of two bloody wars with Germany in as many generations, the victorious Allies hold firm and turn their attention towards keeping the USSR at bay.
The UK and US both independently create nuclear weapons (the UK's programme is much more successful in this timeline without having to fight a war at the same time) before Stalin's army is ready to do anything (remember that he wanted plenty of time to arm and was forced into action by the German invasion); thus the Cold War takes a fairly familiar course.
Ultimately, in 2016 the US remains fairly isolationist but with shared principles of free trade and democracy, has close relations with Western and Central Europe. Europe is dominated by the three victorious powers; what was Germany is split evenly between France, UK and Poland and the three have an alliance similar to NATO (including the smaller military powers of Europe too). Russia is whatever works best for your story - either it collapses in the face of Western spending and its own financial ruin, or the fact that the Anglo-French-Polish alliance has less clout than real-world NATO means that the USSR remains in a Cold War.
Here is a map of Frankish expansion into Europe in the Early Middle Ages:
First, note that the original Frankish homeland is not where modern France is. That is to say, the territorial expansion of the French state started from a place that is mostly not inside the borders of modern France. So it is definitely possible for France to have evolved in a different direction and occupy a different set of modern territory.
This is the 2 minute history version, so lots of truncation for brevity. Basically, Charlemagne split his empire three ways among three heirs. The split was east, center, west as shown: 
The provinces have slightly different names as shown, but the general regions are the same. The problem with the split was that the middle kingdom got diverse territories that were not close to each other. Provence, Lorraine, and Italy were all relatively rich at the time, but not close to each other given the mountains in the way. However, the split did manage to separate the parts that had lots of Latin-speaking peasantry (modern France) from those parts with lots of Germanic-speaking peasantry (modern Germany).
These territorial divisions were reinforced in the Ottonian dynasty (from Otto I) where the power of the Holy Roman Emperor was re-introduced but only for the German and Italian parts. Over the next 200 years, the German and Italian bits became politically consolidated under the Emperors, while the Kings of France consolidated the French and Occitan speaking parts starting from the Capetian dynasty and Robert II of France.
By this time (c 1000 AD), the languages started to diverge, as many of the minor nobility in what was now the German-speaking parts were still German-speaking themselves, but the nobles of the French-speaking parts now spoke a form of Vulgar Latin which was becoming Old French. 200 years earlier in Charlemagne's time, most of the warriors were Franks and spoke Frankish (which was itself a Germanic language).
I glossed over a lot, but the easiest way to make Munich speak French is to change where the Kingdom divides went. Going of the territories of the top map, have Charlemagne divide the kingdoms into Aquitaine-Burgundy (which evolves to be be Occitan speaking), Neustria-Austrasia-Swabia (which evolves to be French speaking) and Lombardy (which evolves to be Italian speaking). Now let the French speaking kingdom rise to power as both the French Kings and Holy Roman Emperors throughout the Middle Ages. Aquitaine-Burgundy get incorporated, just as they did in real life, but bits of Germany like Thuringia and Bavaria do to. The German speakers are restricted to Frisia and Saxony, where they are more or less like the Dutch.
Advance history accordingly, and see what happens!
If you want Munich to be a part of a stable Great French Empire (as opposed to Munich under French occupation), your best bet is a timeline where Napoleon is never defeated and consolidates his rule over parts of Germany (Confederation of the Rhine) and perhaps Northern Italy.
His disastrous invasion of Russia never comes. Something happens in this timeline that prevents it, or makes it have a different outcome. Perhaps the war with the Ottomans doesn't go well for Russia, and the Tsar cannot risk opening another front. Or perhaps Napoleon does invade Russia, but a grand battle comes earlier in the campaign and is a resounding victory for the French.
Regardless what happens, Napoleon rules unopposed past 1814. With Russia out of the picture, the coalition cannot mount a decisive strike against Napoleon, and with both sides weary from war, eventually there's peace. Napoleon rules into mid 1840s, and upon his death, the empire passes to his son, Napoleon II. In our timeline Napoleon II dies of tuberculosis in 1832, but in this timeline his life already followed very different paths and he never contracts the disease.
In this timeline, Spring of Nations never comes to France - there's no Bourbon restoration in this timeline, and the Bonaparte dynasty, while still absolutist monarchs, have the prestige of popular heroes to back them up. And without Spring of Nations, there's never an independent, united Germany to speak of. Over the next 60 years, Confederation of the Rhine becomes an integral part of the French Empire - even if the Bonapartes ultimately have to grant independence to the insurgent Spain and the Republic of Both Sicilies.
It's 1900 now, and we're in for a very different 20th century. The next 116 years are yours to fill out.
Probably partitioning off Southern Germany into France after WW2, both as part of reparations to France for the German invasion, and as an alternative form of the Marshall Plan to create a powerful buffer to Russian/Soviet expansion. Instead of relying on West German occupation by US forces they give over a lot of terrain to France thinking it would be easier to bolster the French military. This is especially attractive if whatever is left of Germany would be under significant military restriction or if the Soviets showed up in East Germany in a much larger force, so the only way to get them to stop wasn't splitting Germany, but eliminating the country all together by giving parts of it over to France, Belgium, etc. The Germans may agree to do this out of fear of being occupied by the Russians.
This is difficult to pin down to a simple change, so I will be content with the outcome of a war, namely: France overwhelmingly defeats Prussia in the Austro-Prussian War
"Now wait a minute," you say, "the Austro-Prussian War was fought between Austria and Prussia, how does France win?" A fine question. While the French remained neutral in the Austro-Prussian War in 1866, tensions between France and Prussia resulted in the Franco-Prussian War in 1870-71. Historically, Napoleon III promised Bismarck neutrality. This allowed Prussia to fight two single front wars, rather than dealing with fighting both factions at once. In our alternative timeline, this non-aggression pact of sorts will not happen (or is broken).
The other aspect of the Austro-Prussian War was the Third Italian War of Independence, in which Austria was defending Venice from Italy. Due to the war against Prussia, Austria was forced to divert forces from Venice to defend Vienna. Italy took advantage of this to ally with Prussia and take Venice. In our alternate timeline, let's imagine that Austria still crumbles in the north but holds fast against Italy in the south.
Enter France. During the end of the historical Austro-Prussian War, France demanded that Prussia relinquish Luxembourg and Mainz. This request was flatly denied. In our alternative timeline, the desire for expansion and the tension between France and Prussia leads to an earlier war, while Prussia is still engaged with Austria. The reduced Prussian strength allows France to make early gains. They also gain the opportunity to study Prussian tactics and organization. This knowledge and slow start to the war allows France to enact much needed reforms to their military structure. Historically, these changes came too little too late, and lead to disorganization. The slow start and high morale from early victories will ensure that these reforms are successful.
To gain more strength for the Prussian front and to maintain peace with Italy, Napoleon III withdraws his forces from the Papal states, as he did historically during the Franco-Prussian War. This allows Italy to seize many of the Papal territories. Napoleon was not opposed to Italian unification, and indeed helped the Italians at times. His support for the Papacy was driven mainly by the large Catholic population in France. We can imagine that nationalism driven by a war with Prussia could override the desire to prevent Italian unification.
Prussia is pushed back and settles for peace, losing their gains in southern Germany. France occupies former Swabia while Bavaria remains an Austrian ally. French unwillingness to cede their gains to former Southern German allies of Austria, combined with the French support for Italy, leads to a minor war between France and Austria, in which France makes minor gains into Bavaria. The pressure of a newly vitalized French military and perhaps a more successful Emancipation of 1861 in Russia keeps Prussian military power contained, allowing France to hold the Bavarian territories containing Munich.
The summary is in bold.
My Scenario takes place around 1700 and is linked to do with the succession of Charles II of Spain. So by 1698, the Nine Years War was over and Charles II of Spain was getting old. At this time Spain was in decline but still an important power that controlled most of the Americas, the Philippines, about half of Italy and modern day Belgium (Then known as the Spanish Netherlands) so the succession was a big deal. Since Charles II never had any kids, it was unclear to whom all the different bits of Europe he owned would go. The main contenders were:
If the Spanish throne went to Anjou, the Dauphin or Prince Charles it would be a huge advantage for those countries, so England and France signed up a treaty in the Hague that partitioned the Spanish Territories so that Naples, Sicily and Tuscany went to the Dauphin of France, the Spanish Netherlands and Milan would go to Prince Charles and actual Spain, Sardinia and the Spanish colonies would go to the Prince of Bavaria, who was the closest living relative to Charles II.
Until he died.
The next year.
While Charles II was still alive.
This completely threw of the treaty and so another one had to be drawn up, which the Holy Roman Emperor didn't like and ended up causing a war that lasted 13 years. And that is how the war of the Spanish Succession started.
But that's irrelevant and the thing to look at that could end up with a French Munich is the treaty after the prince of Bavaria died (at the age of 6) that the Holy Roman Emperor didn't like. So it's 1699, the prince of Bavaria has just died and so the European powers gather again to give bits on a map to each other. This was the 2nd Partition Treaty, and it said that Spain, it's colonies, Sardinia and the Spanish Netherlands would go to Prince Charles, the Holy Roman Emperor's younger son, the other bits in Italy including Milan would go to the Dauphin. The reason Leopold I, Holy Roman emperor didn't like this is because he believed Milan was essential for the defence of Austria, as he was also the Archduke of Austria. So maybe in this Alternate timeline the European powers manage to pull together a treaty that everyone agrees with or Charles II lives a little longer. Maybe Bavaria would go to France in return for letting Austria have Milan and all the other bits in Italy. Also, due to no War of the Spanish Succession, France won't be as economically weakened as it was in our timeline. This is actually very unlikely though, as if Leopold I was concerned about France getting Milan, he definitely wouldn't let Bavaria be French as it is right on his doorstep. So let me propose another alternate scenario: Louis XIV (the King of France) accepts Eugene of Savoy into the French Military.(Around the 1670s) Eugene of Savoy was responsible for about six French defeats in the Nine Years war and the War of the Spanish Succession, including the battle of Blenheim in which he virtually won the war against France (along with help from the Duke of Malborough).
For some reason, the US does not enter WWII, or at least not the European Theater. This happens because Germany and Italy decided against declaring war on the US after Pearl Harbor, and maybe even gave some help with the US dealing with Japan, so we, as a country, did not become involved in actual war against Germany and Italy. However, many Americans still want to go to war against Germany and Italy after this, so those who wanted to fight in the war move to Britain, granting it a much larger military, as well as a continued Lend-Lease program so Britain has a good portion of the US economy behind it.
With these changes, the US does not get an occupation zone in Germany, so what was the American portion is now split between France and the USSR. Munich happens to be in the French portion. However, thanks to the US not being there to enforce its ideals, Britain's belief in them is overshadowed by the USSR and France both wanting to get rid of Germany. East Germany appears as a communist Soviet puppet state, and the French annex their portion into the new French Empire, through the Cold War, Germany was just the portion that Britain occupied, which was eventually freed, with it merging with East Germany when the USSR falls.
During the Cold War, the Germans in the French zone are fine with this because effective propaganda convinced them that this is the only way to be safe from communists. By the end of the Cold War, they've just accepted being in the French Empire as a matter of tradition and have stopped trying to be free.
