(my impression is that this changed in the 50s and 60s in response to Sputnik)

While true, it might give the false impression that the amount of calculus taught in secondary in the States has stayed more or less constant since then. There's been a giant disaster of other economic incentives and disincentives that has driven what one might call "calcification", among them the widening gulf between public and private schools, the development of advanced placement classes, updating the GI bill, and so on.

Sorry. I'll get off my bete noire now.