Is Spanish an U.S language since in Aztlan we Mexican-Americans conduct business in our mother tongue Spanish?

You might think that since Aztlan is a Nahuatl word and Mexico is also a Nahuatl word, we all Mexicans are Aztecs.
If you think that, I might think that California, Nuevo Mexico, Arizona, Colorado, Nevada, Florida, Montana, or Tejas, are Spanish words, then all inhabitants in those states are Spanish.