Why? I think corn's enough.
Nope. Absolutely not.
At a minimum, you need balanced amino acids, so corn/maize and beans may suffice. But e.g. Cahokia didn't have beans yet, so their diet got quite impoverished.
You REALLY want draft animals, although that's probably not strictly necessary. You NEED to learn to spread manure on the fields. (Again, that's easier if you have draft animals and carts, the former partly to provide the manure.) Plowing (again using those draft animals) helps, too, but wouldn't be strictly necessary.
You also need all this in place thousands of years ago.
Part of the problem is that it took quite a while for northern cultivars of beans and corn to make it north to the Mississippian areas. Whereas, rice is native to southern China (or nearby, anyway), and wheat was domesticated at about the same latitude as China. Not the case with the American crops.
So. Get the 'three sisters' package up to Ohio in 2000BC (how? I don't know), bring Llamas up from South America, while using Muscovy ducks and turkeys as poultry, and it would be theoretically possible to get that kind of development in the Mississippi basin by now.
However. Look at Europe. THEY had the crops, and the time, and never developed the population density that China did, so there's got to be other factors involved.
Edit: Oh. And you need clothing, too. Having domestic mammals (like Llamas) helps there, as does having breeds that produce wool (Alpacas, say). Cotton would be another great idea. Unfortunately, I don't believe that there's anything in North America like flax/linen - that produces decent cloth in the north.