Fairly poor, given the numerous missed potentials and opportunities for civilisational development. I'll list a few:
*Extinction of megafauna at the end of the last Ice Age--self explanatory POD
*Alaska was in regular contact with Siberia, but neither the Athabaskans nor the Inuit domesticated reindeer, unlike in the Old World Subarctic where reindeer domesticated occurred at least twice over two different subspecies.
*Polynesian contact was minimal--they did not settle the Galapagos where they could have formed a good trade route with the rest of the Pacific and transmit their own agriculture.
*Large states collapsed from bad luck and bad policy--Aztecs and Inca are the most famous, but the Purepecha certainly had a chance too, possibly an even better one given their position and government structure. I think there's a real chance that an unsuccessful Spanish conquest creates a Mexico+Central America+Andes that resembles the East Indies in terms of polities and intrigue, where Europeans are dominant but only control certain trading posts and coastal areas.
*The Vikings did not introduce the few diseases that could plausibly survive the trip across the sea like chickenpox/shingles, mumps, and whooping cough. This would have altered indigenous practices of dealing with epidemic disease and led to at least some immunity against diseases that impacted fertility/infant mortality as well as killed plenty in their own right (chickenpox in adults can be very dangerous and deadly).
*Better use of irrigation, crop rotation, fertiliser, and insecticide (in this case especially nicotine from tobacco farming). Soil exhaustion and salination of the land devastated centers like Cahokia and the Hohokam civilisation not so long before the arrival of Europeans. Agricultural pests seriously harmed farming among the Iroquoians and is why they moved their villages every generation or so and more importantly hindered continued population growth, but they used only minimal techniques of preventing this and did not use tobacco as an insecticide. In the Pacific Northwest, although potatoes had been grown by Amerindians since the late 18th century, they were reluctant to incorporate slash and burn agriculture and other techniques to improve the yield of their crop due to the effort it would take and no doubt cultural concerns.
*Sweathouses appear to be very bad for handling introduced diseases like influenza, smallpox, and especially malaria--if there had been earlier epidemic diseases like chickenpox, then sweathouses may have been discouraged in certain cases. This would save a significant number of Amerindians in northern California, Oregon, and Washington who suffered from a major malaria epidemic in the 1830s which utterly destroyed some of the densest populations on the West Coast (much to the delight of some white settlers who feared it might be impossible to seize their lands).
I believe under a native state, disease would not have been as severe over time (although far worse than the Black Death) and they could have successfully either modernised or ended up akin to those states of India, Southeast Asia, and Africa subdued by Europeans where despite the hardships of colonialism, the native culture would have persisted and there would not have been near-total replacement. It should be noted that in many areas (the Gulf Coast, Atlantic Mesoamerica, Central America, Brazil, etc.) there would be an inevitable influx of African slaves so formation of Miskito-like ethnic groups and even states is likely, although I could just as easily imagine a rich native ruler importing his own African slaves to replace peasants who have died off. Because of population density, Mesoamerica and the Andes are most likely for this, and I'd love to read a TL of how a Southeast Asia/India-style colonised alt-Mexico or alt-Peru would function.
Survivors do tend to carry immunity. Maybe if it was progressive, ie one after another instead of all at once. If smallpox burned through America in intervals (The Vikings bring it, then the Malians, then the Spanish) the mortality lowers each time. You just need to up the amount of pre-Columbian contact form 1 to something big like 11 with enough time in between. Crops can help with rebound time. The population would wax and wane but won't die as much with Columbian contact.
Most of the New World does not have the population density to sustain endemic smallpox, ergo it becomes like Iceland which also did not have endemic smallpox for a few centuries. And smallpox is not the only disease given there are a host of others. The Vikings did not have smallpox, at least not in Iceland.
Another to consider is why can't a disease like cocolitzi ravage the Old World I wonder.
Because cocolitzi was very likely an Old World disease. It was a specific strain of enteric/paratyphoid fever that due to the conditions in Mexico in the 16th century exploded in prevelance and especially lethality.
Absolute worse case scenario.
Like I don’t know what else you can call what happened to everything that happened to the natives ever since Columbus came down. Besides genocide, which all of this was.
Also how can seriously anyone vote “best case scenario” here?! Like hello????!??!!!?
It wasn't entirely genocide because the deaths of people from disease who had never even seen a non-Amerindian person cannot possibly be genocide. And it gets really hazy when you have Amerindians themselves committing genocidal acts on other Amerindians because they had better access to weapons and resources. And it's pretty clear it could have been much, much worse since the rhetoric of 19th century "Indian fighters" suggests they'd have rather straight up killed all of them rather than the government's solution of pretending to honour treaties only to the degree they could confine them on inferior lands and forget about them.
