I don't think so. Being able to gain lots of cheap and even essentially free stuff from the rest of world has merely displaced domestic labor for the most part.  If the US can't immport as much cheap stuff from abroad it will have to make more of it at home, which, due to abundant natural resources, knowledge, and social assets, the US can do quite well.  Imperialism doesn't benefit everyone -- it benefits the people who go into that line of work. (And it can be rewarding work in more ways than merely economic, so I am not saying this with cynicism.) But why have working people in Germany prospered so much?  Largely because Germany has been deprived -- by the US and Russia actually -- of being able to do the kinds that the US has been able to do, so it made stuff at home and now exports that stuff even with high labor costs.

I am usually one who defends the Pax America project in general, mostly because of the globalization it has allowed and which will probably not continue without out it.  But I do think that the US economy, and especially its working and middle classes, will see their prosperity rise quickly and significantly in response to US withdrawal from world governance activities.