Fallout New Vegas also has it's own very special ambiance as well, it has a nice jazzy, blow your caps on anything and everything feeling. Just being in the midst of all the neon is quite enjoyable but engaging in the activities at the casinos and along with the inhabitants gives it a nice fun feeling. But I guess Las Vegas is already like that.
What I am saying is, lets throw some old world international spice in there. You can very much tell that the Fallout games are very patriotic, with all the discussion of the "Old World" and the war. Well the excitement the US brings to the Fallout caravan table has died down. We've already seen the forlorn monuments to industrialism such as the remaining casinos, brothels, US landmarks, and more but there are only so many interesting landmarks in the US. I mean, we've already hit DC and that was just practice. Now we're in Vegas and even that seems a tad dry.
It'd be cool to take place with all of the foreign monuments and memorials around the world. I mean, I'd love to see Buckingham Palace run by a bunch of rogue AI robots, or that big clock thing being run by ghouls who refuse to accept the end of the world. Heck, if you like the NCR that much you can throw in some EU remnant soldiers or something. Heck, maybe throw in some giant faction of Neo-Nazi's. There's a lot of history in Europe that can be revived by Fallout.
It will be exciting the experience something further beyond the reaches of the USA. We've had enough of Enclave and Brotherhood of steel. It's time for some brand new factions, this time in good old Europe! xD