Well: i'm European, so i have think some factions (europeans) who choose to going in America:

Sons of Odin:
a group of Nordic Europe who decide to find the leggendary Giant and his creatures: A Super mutant behemoth and a big mutant version of some creatures like a Deathclaw and a Mantis)

New European Union:
This pre bellic factions has decide to explore the ruins of America in the hope to find technology and others important documents for the knowledge, but with a terrible figh against some local Raiders, give at this faction the primary mission to rebuilt the america and re make the civilization in the Wastelands.

State of the Church:
after a little travel with the NEU the State of the Church has find a free land to impose their authory and his ideals to controll, conquest and submitt all tribals in the Wasteland, and destroy all tipes of knowledge who can compromise his expansion. But SotC is in a terrible war against the NEU for his interest in this big expansion in the Wastelands

Funny eh? Have you some comments?