but if I HAD to pick one reason
I wasn't asking for a solitary reason.

So pretty much everyone is in agreement that the accumulation of wealth through the various means helped America become the Superpower it is today. How do poeple think the money from the lend-lease program helped America recover from the Great Depression? Everything was all fine and dandy until that pesky wall street crash in 1929. It took more than just money to get out of it, someone had to know how to invest it.

Do people think that the rise in consumerism and the Americanisation of post WWII British Culture made America "fashionable"? Hollywood and the invention of the television, followed by the invention of the teenager for example were massive adverts for consumerism, did these play significant roles in America accumulating it's wealth?