I don't remember the exact number, but I think it's something like 60-80% of international trade is in USD.  A lot of that is probably from the oil sales and such.  Unless the US prints a lot of money or foreign countries switch to denominating trade in other assets, it's very difficult to bring the value of the USD down in relation to other garbage fiats.  That's the whole catch with being a reserve currency, you're required to export more currency than you bring in (a trade deficit and implosion of domestic manufacturing).

The only way Trump can "make America great again" is to destroy the dollar, China style centralized devaluation, print dollars to infinity with hyperinflation, or some other such tactic.  Some people have theorized US currency would be switched into two different units with a new domestic only dollar.  Such a tactic would likely only help the scumbag jewish bankers implement the SDR to take over the world with the SDR as the unit of account, though.  Then 1st world nations would descend into poverty as slaves of the IMF/BIS.