Same thing has happened to myriad empire's in history...look at the USSR..it's collapse had a devastating effect on it's satellite countries however they have by and large adapted. The same thing will happen again
True and people never learn from history. It a fact that all these great empire and country collapse fail to acknowledge a econmic decline, work with and accept another superpower or a new growing one, or it fight to many war.
Econmic decline is a usual thing during the economic cycle, every nation need to curtail economic grow and/or slow down it economic. So that is can fix some of it fundamental problem so it can healty grow in the healty in the future. In US case it choose borrow to fund it growth.
2nd case is China once again. Challageing China isn't going to do much good for the US. Working with on equal term would be much better approch.