In a way it's kind of useless to toss these numbers around. The U.S. media (often in the same article) will use the words "hispanic", "latinos", "immigrants", "migrants" and "undocumented workers" to the point where you have no idea who they're even discussing.
As far as Vicente Fox, he considers any and everybody in America of Mexican descent to be Mexicans, as in his own "people". Most of the Mexican-Americans have no connection to Mexico.
Hey, I just thought of something. Maybe Fox is also including everybody who has/bought/forged a Matricula Consular card to be a Mexican. :)