The best thing everyone can do is maintain low tariffs and try and strike free trade deals with each other. But the consequeces of Trumps Trade war are going to be disasterous for smaller developing nations and their economies. We'll see more poverty, more political instability, civil wars, coups and other unpleaseant activities.
The USA will probably get higher inflation while the rest of the world sees lower inflation if not deflation.
We'll have to find a way of getting through this window of misfortune to the other side, where I suspect we'll all be poorer and less free.