the majority of Mexico, as well as Latin America, is mestizo (Spanish + Amerindian) or largely Amerindian (but still admixed).
[Source]. Mexican culture is a blend of both Aztec and Spanish; you can't separate the two.
Very few countries, like Peru and Bolivia, have large populations of pure indigenous people. They've either been intermixed with the white conquistadors that settled there or have been killed off like in America. The former is what happened in Mexico.
I know there's this white/black thing among Hispanics depending on how light they are, but even the lighter skinned ones look obviously admixed with Native American and foolishly claim to be Spanish/white. Jessica Alba is only a quarter Amerindian but makes her look like a typical latina, not your average white person you see from Spain or other areas in Europe.
Also, it's worth noting that Mexicans can also be part African too. It's not a rare thing