I'm not a specific talent but I was a globetrotter having choose a different country than my original one. Some aspects I've valued and I still value:

- country stability, in term of internal and external projection (I would not look for a country about to go to war or suffer a civil war if I can) witch migh be counterbalanced by...

- ...country population, a population I trust or not, detached or not form the country ruling cohort, meaning mean corruption, attitude toward others, conformism etc;

- current fiscal policies, a high heritage tax for instance is a very BAD point, I can accept only if I know how to escape;

- climate status and possible evolution, orography, food production potential to nourish citizens in case of deep crisis etc;

- scholar system, a free one vs a paid one, an open one vs a casts based one;

- a balance of forces between the public and private sector, when one of both prevail the eventual current stability will not last longer;

USA for me might be partially attractive:

- in climate, orography, food production potential, they are safe;

- in terms of overall stability they are not so much stable, even though not more unstable than many others;

BUT:

- the fiscal system is very oppressive to my eyes;

- the private sector essentially is the State;

- the scholar system have some positive points, like a presence of talents, even if they are declining, but it's largely a cast bases system, and overall not attractive at all;

- the health system is good enough to be annihilated in a thermonuclear heat;

As an western European what can I get from USA? Some beautiful nature, but a byzantine bureaucracy, a very bad health system, a bad scholar system, a private sector more and more similar to a corporatocracy where the "American Dream" was a distant memory.

Trying to imaging a Chinese talent why exchange a growing, technically, industrially active country for the USA? Oh sure China future due to their demographic imbalance is essentially doomed, but not tomorrow morning. It's a bit like Nazi German of the '30s compared to the USA '29s disaster. Very similar for many aspects, but in a totally different shape.

Trying to imaging a Japanese I think Japan is doomed for many reasons but still being from Japan I can hope for better chance than facing a big switch to a totally different country with a similar corporate sector imbalance.

Maybe an Indian might decide to go for mere climatic reasons and chaotic, corruption level of the country itself.

I can keep going but the whole point is that USA was attractive because they was very active and they pay well (this is still valid today, but less than the past), now they a are a giant finance machine still with natural resources about to go to war to save a financial system that can't stand. Of course a vast country is many things, but that means at least civil war or significant risk of it. Not interesting for a life choice in a turbulent time.

IF the public came back to the cold war model of public funded research lead by researchers not by managers pretending to design the research itself and the researchers are just another kind of Ford model workers or while they have many interesting aspects those are not enough.