Well, according to the wiki's lore, there was an event known as the resource war with the middle east, which culminated with a short nuclear exchange prior to the war which raised fear of nuclear weapons. Since Europe depended on Fossil Fuels, when America invented sustainable fission power it bankrupted a large part of Europe and made the war they had waged near utterly useless. Many European nations were dropped into civil war over the remaining eonomic interests which were (???) and that went on until the Great War, though I don't think this is fully confirmed canon.
After the Great War, it doesn't say. It doesn't say which European nations used nuclear weapons during the war, so who knows, maybe they weren't as badly damaged as the US or China? Though they were still involved so I dunno.
I don't know if a European Fallout would sell as well. Society in the Fallout universe was very introverted, so Fallout in England or France wouldn't have very many of the same items or brands like nuka cola and such. I don't know if it would be as fun...

Well I basically went off on the locations of nuclear power plants and the likelihood of them getting destroyed which would cause a HUGE effect on Europe. Even if they didn't get targeted directly there's always a case of miss fire. Despite that it might never happen game wise, it's still an interesting topic to debate on.

I'd imagine Australia has quite literally become a walking mad Max Movie, and New Zealanders are blissfully ignorant of the war and carrying on life as normal.

@IRORIEH While it may not be remotely similar to the products and backstories of companies and services that the United States had, it would still be an extremely fun type of game to dive into. Sure, people would have never ending comparisons between the Fallout in the US and Fallout in Europe, but overall i think it wouldn't be any less fun, just different.