<p>The NCTM standards changed quite a bit in the mid to late 1990s and that’s when I think that proofs got tossed out the window. If you look at the typical college math curriculum today, I think that you’ll find that there is very little done with proofs in Calc 1-3 outside of theory-oriented honors courses or courses specifically offered as theory-based. Even these courses may be designed to be taken after taking a regular non-theory course.</p>
<p>Proofs are typically seen by computer science majors in their discrete math or similar.</p>
<p>I didn’t take Geometry in school (studied on my own) but our high-school calculus course was proof-based but that was back in the stone-ages.</p>
<p>The part about “US students don’t do proofs until after calculus” is correct. Take a look at any of the current crop of typical university calculus books and you’ll see this. BTW, the percentage doing proofs after calculus is probably pretty low as students outside of STEM usually don’t take anything more than Calc 1, 2.</p>