>The whole "maybe math is too hard and we should just make it optional or dumb it down" that I have seen in US was just not something acceptable or plausible as a policy in that system.

Growing up in Europe, while preparing for college access exams, my teacher recommended American textbooks for self study.

His reasoning was: "they have the smartest writers in the planet creating textbooks for the world's dumbest students".

It was a stereotypical joke, of course, but I think there was something to the thought. There's a great combination of STEM talent and a cultural expectation for not letting people behind. The latter probably sucks in classroom settings, when you're stuck at the lowest student's pace, but it works for self study material when you can freely skip and advance.

American textbooks are the thickest, heaviest, have the most pages and have generally more comprehensive coverage that is better for self-studying.

For example Gregory Mankiw's Economics textbook is 800 pages.

Russian economics textbook by Tarasevich is 374 pages