I would point you both to the story of the negro Yanga in Veracruz... he succesfully fought the Spaniards for the freedom of his people... because Yanga was helped at times by various Mixtec & Totonac peoples.. the Spanish decided to grant Yanga's people their freedom and raise them above the Natives in the Caste system.

Let me point you in the direction of the "Pinturas de Castas" which were the tool used to enforce the Social Hierarchy. One thing you will note is that there are two distinctions for Native Mexicans:

a) Indio(a) you can see them depicted in Noble clothing. They are really referring to the descendants of Pre-Hispanic nobility which were largely given the same status in Spanish life. In fact, in you Spain there is still a nobiliary title known as Duke de Moctezuma which are descendants of Aztec nobility who were "invited" to Spain and spread throughout Europe... as well as descendants of La Malinche... and some highly accomplished Natives that weren't of Pre-Hispanic noble caste such as Marcos Cipac who painted the Virgin of Guadalupe image now sitting in the Basilica (considered by many art critics to be more or less equivalent to the level of the European masters of the time).

b) Meco(a) these are Native Mexicans of "uncivilized" tribes or of lower Pre-Hispanic caste.

So you can see that Indios were one rung above Mulatos, but Mulatos were a rung higher than Mecos.

Really think about this... not only did the Spanish create a wedge between Blacks & Natives... but they created multiple wedges between the Natives themselves.

If you want greater proof of the historical "caste supremacy" of Afro-Mexicans relative to Natives... you just have to analyze why Mexico had a Black president (Vicente "El Negro" Guerrero) 40 years before having its first & only indigenous president (Benito Juarez). It was only after the Mexican revolution, "La Raza Cosmica", the restoration of Chicen Itza & other ancient sites that Native Mexicans regained greater presitige than Afro Mexicans. In fact, Carlos Fuentes even elaborates on this them in "La Muerte de Artemio Cruz"

With regards to violence between Afro-Americans & Mexicans in the U.S.... if you go to South Central L.A. and do an ethnography of recent Mexican immigrants you will find that the vast majority have come from Oaxaca where today, there is great tension between the Afro-Mexican communities and their Zapotec, Mixtec & mestizo neighbors... I think alot of these tension is a historical holdover and does spill to the U.S. as many of these migrants are frankly speaken... quite racist & prejudiced towards Afro-Americans.