Okay, here's the deal..
The WHOLE world could not have been wiped out after the war besides those people who found shelter.
Surely then there were nations like China and others who had a post-apocalyptic plan for re-settlement in the lands they salivated over before.
Somebody tell me why there are no foreign occupiers or new colonies.
The human race would breed leadership figures again SURELY.

Most likely because most other nations were in [censored] condition before the Great War.

Why?

1. The Fallout Intros make it pretty clear that the whole world was nuked.
2. Europe and the Middle-East had been in a 20 year war of attrition before the bombs were launched and were economically destroyed.
3. Please explain the logic too me in having foreign powers sail all the way over to establish permenant settlements when their own lands are probably still massively divided and under-populated. Leadership figures have nothing to do with it.
4. Marge Lebarge, there's a whole settlement in San Fransisco built from the Survivors of a CHinese submarine, Allistair Tenpenny...

Even if someone else got on their feet, why would they even want to visit America? It svcks there.