I thought they were indigenous.
Hardly anyone’s oldest ancestors were “indigenous” to where their own generations closest to them have lived. But all folks are “indigenous” to the earth.
And as far as the “Latin” cultures of Mexico and South America, as much as they may contain descendants of persons who predated the Spanish in those lands, the post-Spanish-conquest societies are offshoots of the Spanish conquests which subdued all the “indigenous” societies, and in that sense are no more “native” societies than the other European dominated societies of North America.
Lastly (while I am ranting), neither the society of the Mextecs, nor the Aztecs had a social standing and power more than 200 miles north of Mexico City, beyond ancient trade connections and possible ancient connections to ancient tribes of North America - all of whom fought the Aztecs and later the Spanish. The “Latin” culture and the “Mexicans” it brought with it, north of the Rio Grand, dates to the Spanish conquests and not earlier.
You won’t find Mextec or Aztec tribal names in this list of “indigenous” tribes of Texas, for instance.
http://www.native-languages.org/texas.htm