[Karrot_Kream]

Regarding #1 it's because our cities have become hopelessly auto dependent. In the 50s, much of the US was still walkable and nutrition was less easily available. It was hard to see what car dependence would do to human well-being and scaling human cities, but the US is trying to fix these mistakes piecemeal.

#2 was unique to the US. The rest of the world was either in shambles from colonialism or from WW2. Factories were destroyed and the US produced much of the world's manufacturing output. This temporarily gave a huge boost to American industry. As other countries recovered, competition became stiffer. Moreover the US labor market at the time was compromised almost completely of white men, so there was a lot less labor competition. The story was very different for others.