The US has resources available if you know where to look, but children obviously don't, so it comes down to luck with parents (or in rarer cases a very good tea

The US has resources available if you know where to look, but children obviously don't, so it comes down to luck with parents (or in rarer cases a very good teacher). Perhaps the top Olympiad level types get "recruited". But speaking from experience, kids that are in the high 90 percentiles who enjoy math at a young age frequently end up bored in a typical classroom and eventually disillusioned with the subject - not provided additional resources. By high school one can start seeking out their own resources, but motivation to do math specifically is harder to find when you've considered it a boring subject for 5+ years. And there is definitely an advantage to being introduced certain concepts at an elementary school age. So the US approach absolutely differs in how it handles early math education for the vast majority of students, not just for the average student. I wish I learned math in the Russian style as a child, and moreover I think US math has this problem moreso than even other subjects here. Humanities classes generally have less mindless repetition and early childhood teachers could easily recommend advanced books in a way they really couldn't for math. In many schools the same teacher will teach every subject until you hit middle school! So it is no surprise they don't have resources to give to advanced students, as a lot of them dread math themselves.