It's difficult to imagine the United States being fundamentally changed overnight, but, that's what would happen. The specialists, all the professional jobs etc, in a world wide system of government those jobs don't have to be here, especially when most of the citizens are culled. Those important positions will not be needed. The immigrants are used to worse conditions and will put up with it all because what they will be given here is leagues beyond what they had.

I hope that makes sense I just woke up lol