Speaking of systemic teaching issues, the only thing worse than math is physics.

I was able to do calculus at 10 yrs old (the reason I know that is kind of a long story), yet even at 20 years old I struggled to understand how it was taught.

Physics is worse because everything is always taught as an aprocryphal story about who discovered it and how. And then hand-waved away with math whenever questions arise.

Having noticed systemic issues in education systems since my very first contact with them as a child, I would not be surprised if flaws in how education is performed are ultimately responsible for the differences rather than biology.