In a recent interview, Fallout director Todd Howard said that Bethesda plans to «predominately keep» the franchise in the United States and explained his reasoning. Although Howard left the door open for non-US Fallout settings in the future, it seems unlikely given the franchise's established theme.
Much of Fallout's lore and world-building is inspired by 1950s retrofuturism with a heavy dose of American culture added in. Additionally, the Fallout games are filled with remnants of cheesy propaganda from pre-war America and take place in and around iconic US settings like Washington DC, Las Vegas, and Boston. However, the recent boom in Fallout's popularity has brought plenty of speculation back to the franchise, with some wondering whether a future game could take place outside US borders. Howard was happy to address this possibility.
During an interview on Kinda Funny Games (timestamp 56:40), a fan-submitted question asked Howard whether he has considered expanding Fallout to new lands, whether that be Canada or an entirely different continent. Although Howard didn't completely shoot down the possibility, he explained that a big part of Fallout is its «Americana naivete,» which the franchise uses for world-building and comedic effect. Howard also explained that there can be a storytelling advantage in leaving far-off lands, like Fallout's Europe or other continents, mysterious instead of revealing exactly what's happening there. So for now, Howard and Bethesda seem content to let fans speculate and daydream about what a post-apocalyptic Europe, Australia, or Asia might look like in a Fallout context, and some fans are already quite far along on those thought experiments.
Fallout: London is a massive, unreleased fan-made mod for Fallout 4 that takes place in the English capital and features entirely new factions and (non-canon) lore due to the sheer distance between post-war USA and England and the collapse of humanity's global network. The highly anticipated
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