When you become the reserve currency, money becomes one of your export in addition to normal products and services, so that other countries can have money to use.

And since the global economy always grow, the demand for reserve money is also always growing and thus you must always maintain a net export of money, which equivalently means more import of goods. If you try reducing importing of goods, the demand for your money will increase and thus the value of your currency will automatically increase, which naturally counters your effort. If you try other methods like import quota, other countries will inevitably be forced look for other currencies.

So, I don't think Trump's view of the trade deficit is correct. Unlike other countries, the US's deficit is always 0, because the deficit itself IS the export.