Sounds like the movie The Day After, when millions of people were cramming the US/Mexican border to avoid the devastation about to hit North America. As far as Americans being welcomed in Central and Southern America, for the most part Americans a nice people, but in light of some recent events, such as The Ecuadorian immigrant who was targeted and murdered in NY because some youths believed him to be a Mexican, the Central/South American people are extremely outraged by this disgusting display of racism and it would not surprise me if in an event of such magnitude - they would turn their backs on the US.