Th question of a “reverse American diaspora” is interesting. america is extremely heterogenous..and traditionally has been held together by the promise of opportunity...based on ready and equal access to cheap energy and food. Our Congress and burocracy appears to be deliberately trying to bind us by eliminating both.
Yep. The fact that some in this thread had their ancestors come here 400+ years ago, and others (like me) are 2nd generation Americans shows that "being American" isn't so much about race or history, but creed. And that is something that can transit to other countries as needed.
America isn't just a physical locality, for someone who's only been "inside" the US for 5 years can become an American (naturalized). It's an idea and a creed and approach to life. It will always exist, but perhaps not within the geographic bounds of the United States of America, if the current Administration and Congressional leadership have anything to do about it!