The real downside is that school is insanely competitive, students study incredibly long hours, and they feel intense pressure to perform well on their exams.
The upside is that the students are much more serious about their studies than in the US, in general.
And when it comes to the levers of power, connections are still what defines future leaders in Asia, not grades. This entire idea of "serious students" are ultimately just a bone to throw to the masses.
This is an unrelated point, is your contention that the US is better off with unserious students? Social mobility / wealth accumulation for the masses does suck in other countries but it's great that people are still seriously motivated by schools. It's a big reason those students immigrant to the US and companies here hire those people in masses.
It's that America has the capacity to fully absorb it's talent so it's not a problem. The reason why other countries have more is because they don't have the capacity to absorb them due to less opportunities so the competition is higher. Many of those "serious" students in China or India will still end working in factory jobs and delivery drivers because they weren't good enough.
>It's a big reason those students immigrant to the US and companies here hire those people in masses
Eh, if they were hiring domestic students I wouldn't say there would be much of difference. Unless if you are running a startup, most of these "serious" students will be just writing basic CRUD apps. Value comes from experience here, not talent. Well, if I was American though, I wouldn't bother competing againt millions of desperate Chinese or Indians for opportunity cost anyways, I'd be going more into law or finance. And those fields are less diverse.
If you do academics only, there's also the phenomenon where getting into the right Kindergarten-level school determines your entire school career. In many countries, your current school is a significant factor of your next school.
Imagine not getting into the right Kindergarten having life-long consequences.
My wife is Asian (born there) and when I told her and her family this they were literally speechless.