They should just work together, DC really felt like a wasteland, while New Vegas, was more like a desert. Reason being of course couse House saved Vegas so it makes sense lore wise.
Last I checked a desert is a wasteland. Just wanted to point that out.
How much progress was made when humans were still in the "dark ages", not much, just like in DC.
The "Dark Ages" is a misnomer because progress was made during that time, far more than given credit.
My biggest problems with Fallout 3's setting: 1) There are no living trees or plants out side of Oasis and later Point Lookout and no agriculture anywhere in DC. I don't care how uneducated the people are or how much radiation is around, that doesn't stop trees and plants from growing.
2) It is the capital of the United States, after a nuclear war like the Great War. DC should have been nothing but cinders, a giant whole in the ground.
3) There are smart people like James and other that can do facial surgury, yet they can't figure out how to farm plants? People in the core region had alot worse to deal with and they managed to figure out basic agriculture.