I understand why people say the whole American aesthetic is played out, but really that's just a failure of Bethesda. Fallout New Vegas did a very nice job looking at the western aspects of American culture as well as how the whole "post apocalypse" narrative changes over a long enough period of time, which is to say nations, not just settlements, emerge. Frankly at 200 years there should be many more large factions than the NCR. Even on the drastically slowed time frame of fallout it doesn't take that long for people to organize. Even fallout 2 acknowledged this. If someone with better writers than Bethesda makes a game there's a LOT more to be explored in the US besides new accents.
Hell, so long as it isn't just fallout 3 but in a different part of the US (super mutants, brotherhood, a main settlement bigoted against ghouls, one radio station of classical tune run by the antagonists who have few if any redeeming features and a fundamentally incorrect view of the state of the wasteland and one run by a secluded DJ with the same 12 songs, an ever-present well organized and equipped mercenary group you have no option of non-violent interactions with, a main plot of finding a lost family member (who is markedly older than the player) and then either completing or destroying their life's work etc.), the standard post apocalypse fare of old abandoned buildings full of useful junk and scattered settlements/factions can still be very interesting in a new US location if done well.
Hell, so long as it isn't just fallout 3 but in a different part of the US (super mutants, brotherhood, a main settlement bigoted against ghouls, one radio station of classical tune run by the antagonists who have few if any redeeming features and a fundamentally incorrect view of the state of the wasteland and one run by a secluded DJ with the same 12 songs, an ever-present well organized and equipped mercenary group you have no option of non-violent interactions with, a main plot of finding a lost family member (who is markedly older than the player) and then either completing or destroying their life's work etc.), the standard post apocalypse fare of old abandoned buildings full of useful junk and scattered settlements/factions can still be very interesting in a new US location if done well.