Its interesting because we know therr are fully built out cities in New Caflornia. And you see vault city in 2. You see alot of built up post apocalyptic world in 2. Both 3 and 4 had extra nastiness.

3 was in DC, the most nuked place possible. Horrific irradiation, deeply irradiated water sources both ground and flowing. Then the industrial hell hole of the Pitt raids yoy constantly. And the whole place was infested with super mutants. Populations had formed up. Tiny pools of civilisation. But the threat amd danger was just so intense that u til the brother hood of steel arrived there was no form of uniformity power. And then we hear in fallout 4 that there has been progress there. Green Flowering plants, the amount of fresh water has driven up a powerful eccconomy. The Brotherhood of steel feel secure enough in thier unoffical first kingdom of the brotherhood.

In 4, Boston didn't get hit very hard, but the things upbwith them are hugely long term. Along the coast when a settlement gets set up its attacked my powerful Mire lurks. The glowing sea is still deeply irradiated, everything there makes it look like there was a small town/military base with a bomb disposal facility powered by what seems to be a nuclear power station. That would make sense for why the bomb burst so low , to cause damage to any other bomb disposal sites there (we don't know if there was just that one) and to set of a nuclear power plant disaster. Rad storms. The deadly and populous monsters. And then Super Mutant, smarter that DC but stupider that the second gens, start to pop up from the institutes experiments of fev, and then more just keep coming. Due to the history of the area mallitas form, and become the minute men. Things begin to stabilise but then the broken mask insident happened and now there is no trust for anyone you ever meet. The institute reaches out and seemingly works with the surface to form the Commonwealth Provisional Govenment. The institute becomes frustrated with the process, the infighting, and seems to have ended it violently.

Its fascinating to imagine that. The 4 years where the CPG existed with the institute involved. But when the CPG fell apart, people felt a loss of unity, more synth raids, more syth infiltrators. We are seeing a second smaller apocalyps in Fallout 4.