Between SK and China, SK's per capita income is not far off from US but China's is. I am surprised China is able to compete better than US purely on financial might.
This means for the whole waiting period you need to be employed (in a job that's related to your degree) or you lose legal status.
Compare this to Canada where you arrive with permanent residency, have good healthcare and don't have to worry about losing your residence. Easier to put down roots.
The best deal is for those who earn their stock grants in the US and make a mid-career move to Canada. They start with a good asset base.
The stock grants in US ones definitely are better off, a lot of Europeans also use this and go back.
For Chinese, it's becoming more and more attractive to just stay back (current geopolitical tensions aren't helping).
If you're a EU citizen, grad school in the US is not that attractive comparitively unless you're specifically targeting a lab. Over there you have flexible options like doing a PhD through research projects at work (some govts even give you a subsidy for this). Full time grad students have decent benefits too.
For Chinese, I think there are a lot of other strong reasons to stay back. As I understand from the amount of research coming out of their unis in mainland, they seem to have improved a lot there. Also, R&D in some industries reaching on par to Western counterparts, with jobs paying quite well in big cities, so little reason for them to move away from their homeland.
More than a dozen of my friends who graduated at the same time did similarly, both those who went on to grad school and those who went into industry. This wasn't because there weren't options for us in the US — we all had choices. The honest truth is that, among those bright people I knew in undergrad, the large majority (Americans and international alike) were wholly disgusted by the US in recent years, and being unable to effect any change, they left the country.
As for myself, I have avoided any position that requires me to move in the US. I take a substantial cut because of COL adjustments, but I'm not that interested FU money.
I think the cutting edge stuff is getting less pronounced now because of either global offices/remote or ease of access of resources anywhere.
If you make 1000000 but all of that does down the drain because the country you earn it in doesn't have common facilities available you end up with a pretty bad bottom line.