What he's suggesting is that the US Government should use its enormous leverage to make the Mexican government treat Americans as well as America treats Mexicans. Did you know, for example, that Mexico has a Restricted Zone in which Americans aren't allowed to own land?
And I suspect that if the Reconquista advocates somehow did get their way, and the Southwest United States became a new Northern Mexico, we'd soon have illegal immigrants crossing over into Kansas and Oklahoma for opportunity, because the Mexican political culture would have ruined things in Arizona and Texas just like it's already ruined them further south.
So maybe we've been thinking about this the wrong way. Instead of worrying about Mexicans invading America, maybe what we need is for the United States to annex Mexico.
Oh, we don't need to turn Mexico into a state, or several. At least not right away. But as part of any immigration deal, the United States needs to demand reform in Mexico. Serious political reform, and serious economic reform.
And reciprocity. If we're going to make it easy for Mexicans to come to the United States to live, work, hold property, and get public benefits without too much paperwork trouble, we need to make it easy for Americans to do the same in Mexico. Right now, as several people have noticed, the environment there is considerably less friendly to foreigners than America's is.
But as the Mexican government has been free to express opinions about how the United States should set immigration, economic, and educational policy, it seems only fair if we do the same for them.