A note on nomenclature: since there appear to be divided opinions among absolutely everyone involved, I’m choosing to use “Anasazi” to designate the dominant south-eastern Northern Native American cultural group on the basis that even a hostile Navajo term is less objectionable than even a relatively neutral Spanish term, taking the history into account. Besides, Spanish is not a dominant language in the region, in this AU; in fact there doesn’t seem to be a dominant language except quite locally, and if the etymology of “Anasazi” really does come out to “scattered ancestors” rather than “enemy ancestors” this is a bonus because that fits pretty well with the history tweaks I want to make. The tags, however, will use both “Pueblo” and “Anasazi”.
History that is known or theorized currently: Anasazi culture along the northern Colorado and Rio Grande rivers was quite advanced and included a significant body of astronomical, architectural, and agricultural expertise, as evidenced by archeological findings. There are some indications it had a very complex and sophisticated social/class/vocational system. It appears to have been a city-state culture in many ways, each city independent to itself but sharing a cultural continuity with fellow cities and towns in the region. The Anasazi experienced a massive population increase between the 8-12th C., followed by a relatively abrupt collapse and dispersal. Likely causes for this include 1) a period of intense drought (this is the primary contender), 2) exhaustion of the land through deforestation and possibly over-reliance on irrigation, 3) incursion by some of the Numic-speaking nomadic tribes from the west. There is definitely evidence for intense social upheaval around the 12th C., including destruction of religious centers, dismembered skeletons, and mass relocation, though there is no conclusive evidence of whether the violence was due to internal strife, invasion, or both. There appears to be some speculation that the later legends of ancestors who gained great knowledge and power and thus disrupted the balance of nature may refer to this period, which definitely suggests that technology and agricultural methods were blamed by the majority of the Anasazi themselves. Given the rise of cliff towns among the Mogollon people in the 13-14th C, it seems very likely that many of the surviving Anasazi did indeed move south, this cultural mix giving rise to the Hopi and Zuni groups among others.
And now the Global Steampunk version…
12th C: There is no incursion from the west; the population shift is driven by climactic change, famine, and conflict over environmental technologies. Some of the population, however, does not become embroiled in the wars and social upheaval that follow; instead they react promptly in the traditional way to the exhaustion of those particular lands–they migrate. Thus, in addition to the groups that move down the Great River, some also move west into what is now California, and they are far less exhausted by internal conflict. In that milder and less arid climate, the traditions and technologies of Anasazi culture flourish again with relatively unbroken continuity. Because road-building is one of the particular accomplishments of the Anasazi, they also keep up contact and trade with the Anasazi groups that had moved down-river. This results in a widely-spread but still connected network of culturally related city-states from the coast to the great plains and from about the latitude of the Great Salt Lake down to the gulfs, and, as the droughts eases, population increases and the popularity of technology rises again.
15th-16th C: The rise of the Anasazi, and their contact with the Maya, results in a flourishing trade city on the Great Bay where trade from the Inuit and Anishinabek, the Inca and Maya and Aztec, the Plains routes and, eventually, the Pacific sea routes all come together.
17th C: The value Anasazi culture and its offshoots places on stability and continuity makes them a preferred trade partner and mediator, in the west, and the Northern continent’s oldest university is founded in the Great Bay city and attracts scholars from across the continent.