Mind, other countries specialize their students in early or late secondary school, so the differences may not be quite commensurable. A UK, French, or German student going into a STEM degree will probably have taken calculus and linear algebra by the end of secondary school, but they may not have taken an equivalent to America's AP World History. If you told them they ought to take a first-year university course in world history to get into a STEM degree, they'd look at you a bit weird, but this is admittedly how American admissions works.

I also know an American who basically took every available AP course, had a perfect grade average, volunteered in Girl Scouts, won valedictorian of her well-regarded high school. She ended up wait-listed to MIT, admitted with no financial aid to Cornell, admitted with a moderate scholarship to McGill, and admitted with a full-ride and honors to her state flagship school. She took the full ride.

(Also, we met and later married :-p.)

This contrasts with Technion (I did research there), where you could get into the top-flight STEM institution of the whole country just by earning sufficiently high marks in your matriculation exams.

It really does give me the impression that both other countries educate more rigorously at the secondary level, and Americans have a perverse fetish for inhumanly grueling competition. I think this may be precisely the opposite of a good system: a good system would assure that everyone has a very solid baseline, and then maximize the fraction of top talent that makes it through the training pipeline to do the most difficult work.