I wanted to reply to some comment on climate change and the potential shit the US is in once climate change hits them hard but I thought it was not appropriate and didn't post it there. However the thought is that if/when climate change hits the USofA and make them suffer for their current standard of living, there will be a positive thing. They will not be able to cross the Pacific or the Atlantic in such large numbers to pose a societal threat.
Mexico is going to suffer a bit but I am sure they can use the same tactics the US uses to deter that kind of immigration.
Of course there is the question of military use and that is a quite possible scenario given their history. At least they will have the extenuation of fighting for survival. Literally this time.