What is the most important trade resouce for the US?
The US Dollar
Given its prominent position both as reserve and transaction currency the US Dollar currency is the main pillar of US economy.
The enemies of the country would want to hit that.
Advantages that the currency provide
The US Dollar is a currency that is worldwide used both for reserve and for transactions. Countries that have local currencies may use US dollars for their transactions to reduce risks of changing exchange rates. Since it is perceived as a reliable asset it is by far the most used currency in the world with the Euro a distant second.
The advantage for the US Economy is that the high demand for US treasury securities means the US government can borrow money at very low interest rates. US bonds can be sold at a very low interest without risking of running out of buyers.
The same applies to paper banknotes. They can be printed in large quantities and sold all over the world without causing rampart inflaction because they are highly sought after.
Note that this is an absolute dominant position:
According to the IMF’s Currency Composition of Official Foreign Exchange Reserves (COFER) data, the US dollar makes up 6.79 trillions of the world’s 11 trillion in allocated foreign exchange reserves or around 62 per cent of the total.
and also:
Many countries anchor their currency to the US dollar because their trade and investment with the rest of the world is largely US dollar-denominated. Around 70 per cent of countries have the US dollar as their anchor or reference currency. In this context, US dollar reserves are essential to managing the exchange rate.
The 'reserve currency' myth
Political leverage
US economic sanctions have considerable reach because both US and non-US financial institutions are reluctant to deal with sanctioned entities and countries for fear of being either fined by US regulators or denied access to the US dollar payments system. Non-US banks rely on their relationships with US banks and their access to US-regulated dollar payments system infrastructure to effect international transactions on behalf of their clients.
Rejecting the US Dollar
Given the premise of the question all countries of the world would need to abandon the US Dollar as the main world currency and find one or more substitutes. As noted the advantages of using USD are mutual both for the economies of the US and of the other countries but in the OP question it asks to forget about the damage that this would do to the economy of the rest of the world.
There are alternative candidates but each of them have their own weaknesses. The Euro, the renminbi, crypto currencies could all concurr to form up an alternative but they would need to solve their issues first.
- the Euro is weakened by the lacking of a unified fiscal and political system. Euro assets are not seen as a safe haven given the recurrent debt crysis of many members.
- China's renminbi would need to shake off the suffocating control of the State and reach financial liberalisation
Cryptocurrencies on the other hand may reach a point where they may displace local not-so-reliable currencies in the real world. In OP's world frame they may have the necessary qualities to substitute the USD if duly supported by goverments policies.
But it would require a lot of time, a lot of effort in coordinating the policies of countries that have little in common and surely not the "1 year" duration suggested in the question. It would also be a process from where the world would not turn back. A paradign shift that would have major consequences on the world economics and a shift of power.
An effort (and a cost!) of this kind would only be justified if the USA were to go 'beserk' and become seen by everyone else as public enemy #1. Something very unlikely to happen. Most likely if it is the President's problem ways to remove the President would be found.
P.S. Unsurprisingly US policy has always suppressed attempts in this direction. Ask Colonel Gaddafi for instance. Oh right, you can't.