I've always been struck by how much more educated (meaning broadly knowledgable) many non-US educated people I've met are versus their US counterparts. Part of this comes down to selection bias (having the ambition and ability to practice law or investment banking on a global level, choosing to move to a foreign country, etc.) but I think there is more to it (I practice on those levels but do not feel similarly educated).
For the students at the highest levels, the university structure here pushes them to: (i) spend a lot of time getting to 99% knowledge; (ii) spend time on extracurricular activities as a resume filler; and (iii) learn some subjects (especially languages) late. The structure is the pyramidal hierarchy (and meaningful differences in outcome for different schools).
For most students, I think it comes down to weaker teachers, low expectations, and poor explanation of the reasons for education. Also, I believe that almost nothing is learned at the bulk of colleges.
Separately, I wonder how much the income disparities in the US play a role -- I'm especially wondering if teaching is closed off as an option to people who might consider it in other places with flatter income profiles.
I really have no idea but do wonder about how to improve basic and elite education.