White Mexicans are mostly found in the Northern states and some central states, not all mexicans are brown, Spain colonized Mexico, Mexico is a very diverse country, most mexicans in the US are Brown, but if you go to the real Mexico you see lots of Whites, its like saying that blacks don't exist in America, when Blacks make up 13% of the American population, and Whites make up 20% of the Mexican population.
Ethnic groups of Mexico
Mexican states with high european percentage
Nuevo Leon 55.8%
Baja California 30.7%
Baja California Sur 60.5%
Quintana Roo 56.5%
BTW, Mexico has the third largest white population in Latin America after Brazil & Argentina, it also has one of the worlds largest white populations.