To add another thing to this thread, I mentioned before how a strong Mississippia would be a bulwark against colonization, which would likely as a result cut off the Europeans from the west coast. While the east would be numerous advanced states, the west would be split up still into a variety of small tribes. How do you think they would be affected?
I disagree, the West Coast can be reached numerous ways. Balboa crossed to the Pacific in 1513 for instance. Even if Europe discovers a wealthy empire/kingdoms in North America, they'll still have huge interest in India and Asia so the Pacific will still wind up with plenty of European ships. While perhaps the Aztecs are never conquered, European influence will still be present in Mesoamerica, and Europe will want to trade with West Coast Mesoamerican states like Colima or the Purepecha. All Amerindian states will want European goods, and they will pay mainly in gold and silver. I think Spain would lead the way here like OTL, and even if they don't conquer and directly rule as much as OTL, they'll have huge influence, probably control at least several ports on the West Coast, and have smaller native states as vassals. This means something like the Manila galleon is still viable (since Spain will still be active elsewhere in the world) meaning Spanish ships will follow a route passing Cape Mendocino in northern California and at times drift as far north as Oregon. Spanish enemies like England and the Dutch will follow these Spanish ships, leading to more European presence on the West Coast. Hell, I could see
more European presence since Spain won't have a total monopoly in the area like OTL and native rulers and nobles might become wary on becoming reliant on the Spanish along with their irritating tendency to send Jesuits and other missionaries.
As for the West Coast, that's an interesting question. A
lot depends on what happens in the Southwest. We can assume a tin trade will occur which will certainly enrich the Southwest. Agriculture will spread to Southern California millennia before OTL (IIRC there is some evidence of it, related to contact with the Patayans) which in turn will be adopted and bred for the unique climate (dry summer) of California along with other Mesoamerican plants. Hohokam-style canal-building will help immensely. Over time, this will result in strains of maize more tolerant to the climate spreading north which will slowly be incorporated into local societies. There will be another wave of maize farming spreading north from Utah. OTL there is evidence that at least one or two sites in modern Idaho cultivated maize. It never spread to the Snake River Plain (and beyond the Plateau) since it was simply too much work and too little gain compared to traditional fishing, hunting, and foraging. But TTL presumably Utah is far more populous and with better yielding strains of maize and with some canal building. So maize agriculture has two routes of penetrating to the Northwest and with it the necessary canals for making farming productive on the Columbia Plateau and Snake River Plain.
Other Mississippian crops TTL might spread too. "Wild" rice could be grown with irrigation on the High Plains and might spread to the Snake River and from their westwards. Sunflowers and sunchoke are very good choices to spread west. Goosefoot certainly could spread too. Once agriculture emerges by giving a good additional source of calories and nutrients, it could certainly be intensified. The productivity of salmon fisheries in the Northwest do give some leeway for experimentation.
If we take this spread of agriculture around late 1st millennium BC, then we're going to end up with some serious cultural development in both Northwest Coast and Plateau areas. Hunting and fishing will still be hugely important but I bet at key fishing spots like Celilo/Wyam, Willamette Falls, Priest Rapids, Shoshone Falls, etc. they will experiment with horticulture of maize, sunflowers, squash, and goosefoot. Key native crops like camas or biscuitroot (
Lomatium, a very diverse genus which could allow for lots of hybridisation and domestication of a new species like with amaranths) might become incorporated in this system, it's evident that OTL American Indians tended to their camas patches, except this TTL they may become fully domesticated. In the wetter areas of the Northwest wapato would be incorporated into this system. Domesticated geese and ducks would be brought from the east to give an additional source of protein. There would be a great benefit to places on the Plateau which didn't rely on fishing but instead foraging and hunting which are often overlooked in the archaeological record due to their smaller settlements. Metallurgy would spread as well by this route. California and the Northwest is rich in gold, silver, copper, and lead, and OTL copper was already a valuable metal for religious purposes. If indigeous sailing develops, it will eventually arrive in California and spread north.
How far north would this extend?
Sagittaria cuneata grows as far north as Alaska, Yukon, and the Northwest Territories and would be incorporated into the wapato horticulture system. Cultural exchange among Amerindian tribes was common, so a horticulture or domestic strain of
S. cuneata might be adopted by Salish peoples and from there spread to Wakashan peoples and up the BC Coast in that interaction sphere (including inland to Athabaskan cultures). The northern limit would be the Tlingit of Alaska who might supplement their diet with some fields of
S. cuneata. However, other cultures like the Athabaskans and Aleuts would adopt metalworking too.
Still, we'd end up with far more organised states on the West Coast which would be smelting gold and silver so would be quite interesting to Europeans. Although it's certainly possible that a larger Tlingit population would mean they have more trade to the west (for walrus and TTL gold). There is cassiterite in Alaska (Prince of Wales Island, Alaska Peninsula, Seward Peninsula, and the central part of the state along the Yukon), so there could be a tin trade there if the deposits are accessible and the locals realise that it's a valuable ore to combine with copper. If that's the case, then the Tlingit could easily become a powerful maritime trading culture and keep sailing westwards and westwards, chasing tin, gold, and walrus ivory and perhaps whales as well (assuming some cultural fusion with the Aleuts/Inuit/Yupik). Considering the timescale, we might have the Tlingits arrive in Japan around the same time Europeans are arriving on the East Coast or the Caribbean. The gold and ivory the Tlingits have might spur a Japanese push north (especially since the Tlingits will be trading with the Ainu too).
"Variety of small tribes", no. A variety of languages, yes, but "small", no. It's hard to predict linguistic movements but we'd likely have no "Penutian" languages within the territory of modern California and the Pacific Athabaskan group would likewise be butterflied. We could see some spread of what we'd call "Hokan" languages north into Oregon but it's just as likely that farming would spread slow enough that there'd be little displacement. It's a mountainous area with plenty of local ecological niches, and areas like that such as Southeast Asia and Mesoamerica tend to remain linguistically diverse. The population will be quite sizable, even if they aren't united into large polities. Although there is a potential for large polities, since the Columbia Plateau and Snake River Plain are very suitable for a "hydraulic empire". The Willamette Valley and Lower Columbia has a huge population and few natural obstacles so could unite under one polity, be it a confederation or more centralised state. I'd pick the Willamette/Lower Columbia for a major polity since the land is very rich, there's plenty of oaks (OTL a major source of food for the natives there), lots of marshland for wapato, ducks, and imported "wild" rice, Willamette Falls is a great fishing site, and the mountains surrounding the valley are rich in metals.