I am wondering did Hiroshima and Nagasaki happen in the Fall Out universe, it wouldn't suprise me that Hiroshima and Nagasaki never did happen (one way or another), the terrible side-effects of a-bombs where never being seen 'till the last decades before the great war ..... The second world war did take a couple of more months than in our universe, the Japanse eventually did get exhausted, (pretty much motto never surrender, never give up) and by then the Chinese liberated themself from Japanse opression not even that maybe they even did invade Japan for a while or longer.
I know it might sound stupid but I thougth of this .... The world seperated in the fifties, but why not the last years of the fourties ....