Spanish is a European language too, just like English. If these folks want to return to their real homeland, they need to buy a ticket to Madrid, not Los Angeles.
Many, perhaps most, Mexicans, and South Americans generally, are of indian heritage (Aztec, Mayan, other) who bred with the Spanish. The original Spanish invaders were of European stock, some with Moorish influence no doubt, but not presenting physical characteristics consistent with what we see in Mexicans today.
I think it is safe to say that their "homeland", to the extent it can be traced going back, say, 500 years or more, is Central and South America. Not north of the Rio Grande.