> The other half is, WWII turned the United States from a relative backwater to a military and industrial superpower.

The US was the leading industrial power from around 1880 or 1890, and it became the leading military power in the 1910s (by dint of entering WWI so late that it didn't exhaust its manpower fighting it). It may have been a cultural backwater as late as WWI, but its economic status would have been fairly undisputed. And by WWII, the only question anyone would have seriously asked is if the US or the UK held the throne as greatest of the great powers.

I think if you look at how most people lived, worked, travelled, communicated, educated, etc before WW2 - there was a huge improvement after the war that resulted in lots of development and economic opportunities for the average person.