What is the whole A+ business?

A+ is like a 90%-100% right? I always see americans in movies just getting multiple A+es on a report card, but here in Europe (at least in Belgium) 70% is already good in most middle-/highschools. Having an 80% on a report card for more than 2 subjects is a real accomplishment. And having a 90% on more than 2 is something only 1-3 students in 60 can really do in good schools.

Is this just a myth and do Americans almost never get an A+ on report cards? Or are American tests just easier and that's why you're expected to score better?

Edit: I do not agree with the stereotype. I just wanted to point out the irony of Americans being perceived as dumb but still gaining such high grades. My apologies.