The people who put Trump in office, at great expense, are the people who make money of selling arms. If arms sales go down, they will be unhappy and the president will be advised, his support will be reduced unless arms sales resume.

If a country stopped buying arms, and also stopped by American oil and gas, pressure on the US government increases : no more donations if the big corporations are locked out of certain markets.

Historically, those actions - or their equivalents - have been more enough to get the US sniffing around for other leaders for that country, who more amenable to US interests, and covertly supporting them.

So this country is no longer buying US arms, nor US oil. It might then decide that it no longer needs to work in the US dollar, switch the Euro or Yuan, weakening the standing of the USD as the world global reserve currency.

This would be enough to get them a delivery of Freedom & Democracy by the US Military, or at least coup or assassination.

If it sounds far fetched, the US did this to Chile, Cuba, Argentina, Venezuela, Iraq and Ukraine where they have been interfering with elections for a decade or more