This is the sad reality of it. The U.S. had (still has in many fields) the biggest budgets, best toys, and best environment for bringing in foreign researchers. Europe underfunds science comparatively while China is not a great place for foreign talent to move. Without the U.S. funding, we all lose.
Gerrit Bruhaug
There's a persistent fantasy that maybe some other nice countries will start mass-hiring US scientists.
That's not going to happen. A few high-profile, big name researchers will get poached, sure. But most countries, including some very nice ones, are underemploying their own scientists already.