Just speculatin' here....
The latest edition of "Mathematics Magazine" from MAA lists the top-scoring students in the last USA Mathematical and Junior Mathematical Olympiads, and the names are as follows:
Timothy Chu, Calvin Deng, Michael Druggan, Brian Hamrick, Travis Hance, Xiaoyu He, Mitchell Lee, In Sung Na, Evan O'Dorney, Toan Phan, Hunter Spink, Allen Yuan, Yury Aglyamov, Ravi Bajaj, Evan Chen, Zijing Gao, Gill Goldshlager, Youkow Homma, Jesse Kim, Sadik Shahidain, Alexander Smith, Susan Di Yun Sun, Jiaqi Xie, Jeffrey Yan, Kevin Zhou
One can't help but be struck by the degree to which names of Oriental and Asian ancestry seem to predominate this list of USA Olympians. Even in my own college math courses on the west coast 40 years ago I saw such a predilection; certain foreign nationalities seemed to have a 'knack' for math and analytics that Americans often struggled with. One wonders how deep/real these differences are, and if they are culturally-based or even possibly have a genetic component... or, I'd be curious how many of these students early-on learn foreign ancestral languages in addition to English, and if early exposure to certain languages predisposes one toward a mathematical aptitude or analytical skills in general (in a Whorfian sort of way).
I suspect somewhere out there this has all been looked at, or at least argued over, but don't know if there is a resolution to the notion (and of course the above names represent too small a sample size to draw any real conclusions from, so I'm just wildly wondering out-loud here...). American teaching methods for mathematics have often come under fire in recent times (leaving many young people phobic of the subject), and yet certain students always seem to excel and remain enthused, regardless of method.