Anthropology

was still a village of about 500 people, it relied on agriculture as well as hunting. So it was already predisposed to relying on cultivated plants before corn became a staple of their diet.

I recently read an atticle (sorry I don't recall the source) about Cahokian crops prior to (and layer concurrent with) corn. It suggested that the reason for the late arrival of corn to Cahokia was that corn needed time to adapt to more northern, cooler climates than its origins in the hotter, moister climate of southern Mexico.

The southwest of the current US had corn much earlier. I've often wondered where Cahokia first got corn from. Could have been from the southwest. But considering the temples and layout of Cahokia, it seems likely that Cahokia got its corn from traders farther south along the Mississippi. Aztecs had trading boats that followed the Gulf Coast. They would have traded with towns and villages at the mouth of the Mississippi, who in turn would be influenced by Aztec culture and pass aspects of it farther north themselves through trade, including items like corn seed.

Eventually, the whole area of the Mississippi Valley and the US southeast merged into the Mississippian Culture with religious and structural similarities to the civilizations of Mesoamerica, tweaked to local preferences.