Terminal said
Is the Enclave even still a thing after the events of Broken Steel? I don't doubt that there's probably a few bunkers left here and there, but East Coast/West Coast/Central America Enclave has pretty much had its command structure stomped flatter than all the soda lying around the wastes, and both the NCR and the Brotherhood of Steel have shoot-on-site policies concerning them.
In addition to what Peppermints said, there's also a lot of places a group like the Enclave could survive in to some degree. The events of the first Fallouts and Fallout 3 only cover a tiny area of America. There are no doubt a thousand places in the lower 48 for the Enclave to hide. And don't forget, in this world the US annexed Canada which'd roughly double the landmass to chunk down US government bunkers for surviving elements of the Congress, White House, or Military to hide in. Not all of them could have fled out to a oil platform in the middle of the Pacific.
There's enough room to apply hearty fanon. And ultimately in a game as morally open as Fallout (more-so given I don't think any events from Fallout 3 or New Vegas are confirmed canon as Fallout 1 and 2 are) there's a lot of room for fan-based alteration to make a more "custom" world, even if based in the themes, images, and over-all story of Fallout.
For all we know, Dearborn could just as well have spawned a satirical version of an Islamic state in Michigan, south of Detroit. Given Fallout's habit for dark humor it could be a thing. And the closest that area is ever mentioned is from a slaver in The Pitt who I remember asking you if you could possibly be "From the Eeries" (which I take a references to Lake Eerie).
