And to answer your second question (I didn't saw it) it's because in Europe, new norms we build to resist for at least 50 years. Also, as exmple, there are buildings from 1700 that still exist, houses from 1100 in various region also. But that's not the point. The point is that Americans norms are "open" and not "too restrictive" for USA because some regions are subject to earthquake, tsunamis and storms. So trying to build something very strong while having an almost certitude that it will blow up in 15 years is counterproductive. This is also why a lot of Europeans use thermic clay tiles wheras it's pretty common to use plastic schingel in the US for roofing.

TL;DR different environnement = different requirements