In the southwest it makes, or made anyway, a lot of sense.
There were essentially two groups of people, the Spanish/Mexicans who were Hispanic in language and culture, and the “Americans” who were English in language and Anglic in culture.
Led to some oddities, like black guys being called Anglo. But perfectly logical from the perspective of the Hispanics, who were simply identifying someone as “not Hispanic,” and of the dominant American culture.
I read that Native Americans called African-Americans "black white men".