Haven't pre-Aztec trade goods, for example, been found as far north as Chaco Canyon?
I just pulled my copy of People Of Chaco, by Kendrick Frazier off the bookshelf. Here's what he said about that argument:
"The Chacoan culture, had indirect contacts with cultures elswhere, including MesoAmerica, but it developed on it's own. It's rise didn't require the beneficent help of outsiders. And neither did its eventual fall result from their departure."
I think it is/was Christy Turner at ASU that takes a different view and believes there was an Aztec invasion.(more or less)
Turner is the one who took so much 'heat' over the discovery of cannabilism at some of these sites.