” ... If the land plays out or you get a bad harvest, you have go further afield - which is iffy when your transport is animal based. ...”
The search for food, and its transport to their city, would have been iffier still for the Mississippian culture. They kept no domestic draught animals larger than dogs. No one did in North America, until the Spanish left horses behind, who survived and bred. So everything the Cahokian urbanites may have found had to be carried home on people’s backs, or dogs’ backs, or dragged.
And the farther they had to go afield, the more likely they’d be to encounter groups less inclined to bow to their self-appointed status as religious and secular overlords. Possibly, forage expeditions got wiped out, or robbed of their spoils on the trudge home.
Llamas - the only domestic animals anywhere in the western hemisphere with size, strength and abilities greater than a dog, were confined to South America at that time.
And no one in the Western Hemisphere had wheels.
Ritual human sacrifice seems to have been a central feature of plenty of urbanized “Native American” societies beyond the Aztecs: Maya, Inca, Moche at least.
‘Ritual Human Sacrifice” was just a cover for cannibalism among the upper classes of those peoples. Regular access to protein gives you a lot of advantages over depending on ‘beans, maize, and squash’ to be available in sufficient quantities at the same time.
They had an incredibly large water network for transport- their trade ranged from the East Coast to the Rockies, the Great lakes where they obtained copper to the Gulf and Florida, where Indians dug canal networks for canoes; Cahokia’s people may have, too, though centuries of seasonal flooding would have erased them.
Clubs have been found at Cahokia containing the teeth of Great White sharks; conch shells from the Gulf and Atlantic were carved at Cahokia and traded further west to Spiro, Oklahoma. Mica from the Appalachians was also found. Flint from Texas. And Cahokian artifacts are found all over.