A large developed country with 300 million people is going to be a target for relocation, but I've most certainly seen a very substantial change that does not benefit the US.
There's more people doing startups in their home country. More SV companies running satellite offices outside of the US to court talent that is unwilling to move to the US. More countries that are seeing the value of a strong software industry acting accordingly.
Not all of it has to be Valley-style startups funded by venture capital. There's a lot of traditional industries that don't need that funding model that are realizing that most talent doesn't actually live in California.
By now I know of many cases of people who have moved from SF after being courted through visas who moved back home or to offices in the EU, and many PhD candidates who ended up going to France, Switzerland, Germany and Spain to complete their PhDs, where the academic environment lends itself to a better work-life balance and high quality of contributions.
Mind you, this mostly applies to immigrants from Latin America, who have goals that may be different from Asians and Europeans. Still makes it a relevant observation.