Or it could cause the United States to send troops into Mexico, and the country could get taken over and made part of the United States (a huge effort to assimilate over a hundred million people would be a challenge, though).
Not to mention the huge effort of the American taxpayer to support them all.
They're gonna' love Siberia eh!
Maybe they will stay there and thrive if we allow capitalism to work there. They have plenty of oil, and plenty of other resources, not to mention two beautiful coastlines, and a climate that beats many places. They simply have get off their collective a$$es and work the land, and be able to keep most of what they make. You might even see the flow become net to the south!!