It looks more like 250,000 – 300,000 Mexican immigrants per year. Google results for: Mexico "immigrants per year"
It did collapse - in 1994. The question is: What does a collapse look like?. Institutions don't disappear; they become more and more ineffective. People still get up, put on their britches and go do something. Even China functioned after a fashion during the Cultural Revolution.
We made our way through the great depression.