Actually, if you took a genetic sample of the average Mexican, they would likely have more Aztec, Toltec, Olmec, Zapotec, Tarascan, etc. ancestry then they would Spanish.
You forgot to add blacks to the mix..
Some mexicans are black, some are white..
Some are "in between".. The proportions of "indian", black, and white vary greatly depending on location, history, etc..
Many Indians in Mexico would not consider themselves mexican but indian..
Many Mexicans would agree on the distinction and that is why there is so much political strife and violence, both by and against indians in Mexico..