User blog comment:Callumthered/Mexico beats America?/@comment-32656-20120206091304/@comment-1310192-20120206180800

Though at some point Mexico could have somewhat blocked thhe influx through soldiers or the like-yes, Mexico's army was incompetent, but. AFAIK the Mexicans helped the immigrants to go there so to boost population, and a short crisis would have led to the cease of immigration. Less requirements for Mexicans to receive land concessions in Californiamand more immigration from Sonora, Baja, etc. could've done the trick, no?

But yes, you're right, a plausible POD has to be way back,