According to Aztec legend, they came from far to the north, which Mexican racists take to mean the SW USA and draw the conclusions I mentioned from this "fact."
The Aztecs are fairly closely related linguistically to the Utes and other SW American tribes, FWIW.
There is, BTW, some evidence that the move of the "Anasazi" into their cliff dwellings was related to an increase in Meso-American influence, perhaps even "missionaries" from what is now Mexico.
If the neighbors got into human sacrifice and cannibalism, I'd move into a cliff dwelling, too.
There have been no Aztec ruins ever discovered in what is now known as the United States.
Actually not true. Just outside the town of Aztec, NM there is a large ruin that is called "Aztec Ruin." Nothing to do with the actual Aztecs, of course, but still an Aztec ruin.
At one point, he proposes the possibility that a diet very heavy in corn increases the possibility for madness. Obviously, the southwestern tribes ate a lot of corn, but also beans, squash, etc. But corn became very important to their spiritual practices and some anthropologists think that it's possible that this could have the been the reason some medicine men literally "snapped" and that the cannibalism thing really did happen. If I recall correctly, Childs seemed to think the Anasazi were more closely related to the Pueblo than the Aztec tribes. It's still a mystery. But until I read the book, I had no idea that there were so many abandoned Anasazi ruins ... they are all over the place down here. ANd the one at Mesa Verde was a huge complex of great significance to the region. They're also fairly certain that cannibalism happened there, too. What they can't seem to figure out is why they abandoned these places, but it's possible that the water sources just dried up... as they do in the desert.
I do know that the local tribes will not set foot in those places. They won't even talk about them. They shut down completely if you ask them about it.