The US doesn't have "low standards", it has broader access to liberal arts education than Europe. It ends universal secondary education at grade 12, so the grade 13 (at college) completes the "liberal arts" foundation. European countries simply do grades 12 and 13 in a separate school between secondary school and university, for students that weren't forced out after grade 11.
https://en.wikipedia.org/wiki/Sixth_form_college