You are completely right, US is best in the world in that narrow sense and this is what matters for me.

You see until high school I was studying in my home country, an European one, next I went to high school for a year in the US which had a large population of Asian foreign exchange students. Then I did a year of non-degree studying in China (not very relevant to the discussion) and now I study on-line following a British curriculum.

I saw a LOT of Asians and Europeans struggle with the curriculum in the US. Language issues? For some, yes, but I knew a lot of people that struggled simply because they were not used to the way Americans are thought. I had friends complain that they were doing great back in their home country and now were just average. (I virtually only had foreign-Asian friends, foreigners didn't really hang with the Americans which is another story). And some courses were indeed simply more rigorous in the US than back home.

What an average student in any country learns is how to beat the game, that's what school almost everywhere is about, not about deep understanding. That's why it's enough to change a few variables in the game and those students that supposedly followed a more rigorous course find themselves struggling like my friends in the US.
The same thing happens at average universities. You just have to beat the game to get the diploma. Europeans on average have to beat a slightly more difficult game, big deal.

Do you really think that there is a significant difference? I took AP calc and then “Maths 1” at that British school. The most notable difference? No calculator on the test. Of course, they do throw far more rigorous explanations at you, use fancier vocabulary, give you more trick questions, but to pass the test you don’t have to be much better, you just have to adjust to the game. European students will be as clueless about the simple Epsilon-Delta Proof as American are.
They simply “cram” in a little more to students overseas. (cram as in learn without understanding rather than study hard). I don’t really see an European student being somehow smarter than you’re average American one. Trust me, after travelling a lot, getting to know many cultures average people seem average everywhere and extraordinary people are always extraordinary[1]. US happens to produce and draw most of those.

I don't know, I might be going too far with that argument, but I strongly believe that those few top-class people which will be leaders in their respective fields will contribute to the economy far more than having each average person be a little better. As in it's better to have 1000 stupid soldiers led by a genius than 1000 slightly less stupid soldiers led by a moderately intelligent person.

I'm not saying there's nothing to fix, there's tons of fixing to be done in every single country.
I just think that as a whole country the US should focus on sustaining that comparative advantage in higher education, as long as it has that US is the world-wide leader of education, at least for me.

[1] For some people it takes a lot of time to get to that stage, some might outright disagree with me. Most people have trouble filtering cultural differences and often see falsely assume that people in a certain culture are just “better”, because they use their native benchmarks to judge people elsewhere and the other way around.