Do you speak American?

I really enjoyed watching the video "Do you speak American." I've seen that documentary before but I realized that each time I watch it, I learn new things from it. The point that stuck out or was "new" to me was in this viewing of the video was the point about shift in preference from British English to American English. I find it interesting how World War II marked the shift in language preference in the country. Although there were many allied powers involved in the victory over Germany and Japan during WW II. I wonder how much of the shift to preference to American English was connected to the change in the status of the United States in global scene. Unlike many allied partners and the UK, the United States did not have to "rebuild" as a result of the war in regards to war damage thus setting the staget for the USA to be in a better position financially and the amount of resources and presence that was allocated. Moreover, how much did the geographical location (away from the war--with exception of Pearl Harbor) and size of the USA that help to reinforce and build up a more united American identity which saw more value in their "home" variety than that of British English???