My guess would be EUR takes its place, gold will also be used more. I guess what happens is USD gets much weaker and US buying power goes down. Maybe destroying the USD will eventually cause the boost to domestic manufacturing that Trump wanted, since foreign goods will be out of reach. Cut down the forest to kill a squirrel. I'm no expert though
There will never be a boost to domestic manufacturing without some kind of investment. The booms of the 1950's and 1960's were a result of massive government spending in the 1930's and 1940's building a bunch of capacity and researching novel manufacturing techniques and building new tools. If we don't have the morale for that we will simply stop having as many things.
It also included a bunch of women joining the workforce, an enormous baby-boom and brown people acquiring the freedom and prosperity necessary to become consumers. Demographics are always the fundamental driver of economic movements.
Domestic manufacturing isn’t coming back without a thoughtful investment program. A lot of older people still think of China like in the 1980s where it was mostly low-wage, low-quality products but that’s nothing like true now and they have entire clusters of world-class product pipelines with long supply chains which would take a long time to bring back in stages.
The other problem seems even bigger: we don’t have many high-skill workers available, but our wages are high enough that anyone bringing manufacturing back is going to try to automate it as much as possible. That seems like a real bind for the Republicans’ isolationist strategy: exports will be down due to a trade war and a difficult price/value ratio in the areas other countries currently dominate, and if we’re heading into a more automated economy we’re going to have a growing number of people who won’t be able to afford to buy much. This seems like a vicious self-inflicted cycle if it gets rolling.