Quite a few European countries including the UK I believe are starting to develop policies that would help highly educated Americans get citizenship on a fast track scheme. We don't want a lot of scientific knowledge to go away just because America has decided to fall apart. Come work on our particle accelerators, experimental fusion reactors, or join the European space agency. It would be nice if we could have human space flight independent of Roscosmos and NASA. Maybe we could even beat NASA back to the moon, since I can't really see Artemis making any progress anytime soon.

I don't think anyone's got as far as actually implementing any of these policies yet, but they're on the way.

I'm sure China would also happily accept Americans, but you might not want to go that route.