It might be because I have only played a couple Fallout games so I don't know the lore down to the specifics......but the New California Republic is based in California, and the TV series is also based in California. So how is that like saying one planet is another planet? And since it's only 10 years after Fallout 4, I'm not surprised it looks more like Fallout 4 versus the other Fallout games.
The issue is that it shows like a wasteland, but one of the things the NCR has is a GECK(deus ex machina that terraforms and cleans land.) Particularly in the cities, it would be a post-apocalyptic wasteland, but a living, bustling city full of ordinary people.
They have enough industry to make and maintain old world tech like Vertibirds, APCs and Tanks.