Alright then, another question. What would the hypothetical Fuedal era of these alternate America's look like? With Fuedal being applied loosely and not requiring it's adoption in more than one Culture Group.
I don't think that there really would be a feudal era equivalent to that of Europe (I don't think that talking about 'levels' of development is helpful, as it suggests cultural superiority of one culture over another).
In an ASB-sealed Americas here are the changes we may see over the course of 1,000 years, going from north to south:
Arctic and Taiga: Would remain hunter-gatherer. However, as technology develops the populations would grow, peoples might centralize to a degree as they compete over shrinking resources. While I don't think we would see
@DValdron 's "Land of Ice and Mice" timeline become a reality, we may see more intense management of the wild to encourage the growth of edible plants like the ones that take a central part in that timeline.
Pacific Northwest: Would become quite 'feudal' in many places, with elites continuing to concentrate their power as they did IOTL. These elites may enforce the adoption of agriculture on the 'commoners' if potatoes are traded that far north.
California Coast: Would *most likely* remain hunter gatherer. However, ecological or artificial disruptions (such as large-scale slave raids) may force people to adopt agriculture from the East or South, possibly adding domesticated varieties of previously gathered native plants to these foreign agricultural packages.
Southwest: Post-Anasazi, the Pueblo peoples had found a good equilibrium for their agriculture. Without horse nomads to threaten them, they are liable to live quite in peace and IMO would partially assimilate the Athabaskan peoples. I think the apocalyptic strains of religious thought common in Pueblo culture may fade away or lose some of their edge, as long as they maintain that equilibrium and aren't threatened by outside forces.
Great Plains: As stated by other posters, would have agriculture in the river valleys, with a few nomads using dog and possibly llama travois to skirt the edges of the plains.
Eastern Woodlands: A 'feudal' system of elites may rise up again, imposing a neo-Mississippian order. However, the form of control these elites use would be very different from that in Europe-for example, there would be a dominant class of religious ritualists instead of a warrior class and religious class sharing power as in Europe.
Northern Mexico: If potatoes are introduced, it might become a little more agricultural as potatoes are much less thirsty crops than corn, and so more appropriate for the region.
Mesoamerica: Metallurgy would develop further and a 'bronze age' could begin, but ultimately the average person would not have access to metal tools or weapons. A possibility is that larger unitary states will grow out of Aztec-like tribute empires. If potatoes are introduced, highland areas like Chiapas and southern Guatemala may become more densely populated and culturally influential
Central America: More involved in a nautical trade network, acting as an important bridge between Caribbean and Pacific trade networks.
Caribbean: The development of nautical technology will probably see many of the Caribbean islanders drawn into mainland trade networks and material cultures, with ensuing shifts to adapting mainland cultural practices such as the Mesoamerican ballgame.
Andes: IMO the Inca empire will collapse, but it may spread a precedent for centralized states and will leave behind a rich (and useful!) material legacy in the form of terraces for farming and roads for transportation. I expect that the Inca Empire will serve as a rough analogue to the Roman Empire for Medieval and modern Europe for the cultures of the Andean peoples.
Amazon basin: Terra preta agriculture continues to spread, and more of the land is engineered for human needs.
Southern Cone: If agriculture comes eastward, like I said the area is ripe for the rise of a very densely populated agricultural civilization.