IMO Jet (like caps, and like Supermutants; and like Enclave, and like Centaurs, and like Deathclaws ~though they'd be the exception if one should exist)... All of these should have been a West-coast only phenomena, and not have been relied upon for the plot of an East-coast installment of the series. They could have completely broken free of the past isolated setting, and wholly invented the East-cost metropolitan states, and their own local hazards, monsters, and maniacs.
Fallout is actually suitable for an almost Warhammer-like 21st century political environment; with a militarized Pentagon, and access to far more top-tier technology; (and actual US money
).
More so than the combat & rule changes ~This was the chief disappointment [for me]: Lost opportunity for an unexplored sector of the Fallout world with it's own attitudes, and history. One that new fans would accept unquestioned, and that series fans would accept as the other side of the continent, and largely unrelated to the first two games... and one where Jet doesn't rightfully exist, but any number of equally bad drugs certainly could. The Fallout version of DC, 200 years later, could have rightly been a bit like a remnant 50's http://www.youtube.com/watch?v=jTus6TV2eio#t=00m15s, and likely have been really,
really great.