both the Great Basin area and the American East and Southeast hosted fairly well-developed sedentary agricultural civilizations until European contact.
I am not an expert in the field, but a look at your Wiki links shows that both these civilizations basically collapsed before any significant contact with the Europeans for unrelated reasons.
The Southwest agricultural civilizations show a growth/decline cycle going back hundreds of years before contact; it's probably primarily climate-driven, although some features of the archaeological record suggest that warfare's been an issue too. European contact was just another decline, one that they managed to weather pretty well by Native American standards -- their successors are among the most intact native cultures.
The Mississippian culture didn't show that cycle, but it nonetheless was in decline for unrelated reasons at the time of contact (wi...
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