We have for the last 40+ years run a trade deficit, Trump, can't have a positive trade balance and the world's reserve currency. One of those two has got to give.

 The following is from a Australian article.

Enter Donald Trump, keen to make America great again. He views a nation as he does a company, so surplus = winner/good; deficit = loser/bad.

He apparently wants America to replace Germany and China as the world’s leading surplus nation because that would mean winning instead of losing. To achieve that he wants to tax imports at 20 per cent and subsidise exports by the same amount, and renegotiate all the free trade agreements that he says have disadvantaged the US.

But it’s not quite so simple. Trade deficits are neither inherently good or bad; it depends on the circumstances. Not only did the United States get a lot of cheap stuff from China over the past decade and a half, most of the money it spent on those products came back as investment, pushing interests down and creating jobs to offset the manufacturing jobs lost to China.

The fact that the US didn’t use that money very well, and spent it on inflating the price of housing, is not China’s fault.

In any case, Triffin’s Dilemma might have to be renamed Trump’s Dilemma. That’s because if America really does start to run current account surpluses, the whole international monetary system would have to restructured around another reserve currency, because US dollar liquidity outside America would dry up.

The problem was anticipated by Keynes and Schumaker in 1940, when they conceived of a supranational currency called the bancor. These days any new reserve currency would probably be based on the IMF’s special drawing rights (SDRs), which are created from a basket of US dollars, euros, yen, pounds and, since last October, renminbi.

In short, America can’t have the greatness of a current account surplus while retaining the greatness of being the world’s reserve currency. Mr Trump will have to choose which “great” he wants America to be.

Maybe he has already concluded that the price of having the reserve currency is too great: after all, the strong currency has meant the loss of American industry to China and the capital inflow has led to debilitating asset bubbles.

But there are many advantages offsetting those disadvantages. Apart from anything else it means the US government is swimming in cash and can fund the most powerful military the world has ever known. And when the American housing bubble precipitated the global financial crisis in 2008, money didn’t rush out of US dollars as you might expect, and would have happened had it been any other country — it went the other way, flooding into the US.

But apart from that, America’s broad global leadership — its ability to act as the world’s policeman — largely rests on the dollar’s hegemony.

But being a winner in that way depends on it being a “loser” in trade. You choose Mr Trump."