While the American south west was once a Mexican territory, there were never more than a hand full of Mexicans living north of the border. Those people were offered American citizenship, or a ticket to Mexico. Of course they stayed and became Americans. There are no Mexicans in Mexico that have any historical claim to any land in America. Mexico has no claim to the land, and the people that were here, became Americans, and forgot about the oppressive government that had been trying to control there lives. I'm sure their families are very happy with their ancestor's decision right now.