^What did you think Indians ate before white people got here?
You are right about a corn-based diet, which was common throughout all of the Americas. Popcorn, succotash, tortillas, etc, are all traditional American Indian foods. Across North America fry bread (an unleavened bread that is, unsurprisingly, fried) is a common food, and while the recipes vary from tribe to tribe, pretty much every tribe has their version. It is even seen as a symbol of native pride, and this shirt (I actually used to have one!) was made famous by this scene in the movie Smoke Signals
Fry bread can be served many ways...sweet with cinnamon and sugar, with toppings as fry bread pizza, etc. It can be made with sweetbread baked from flour made of dried and ground berries. It is pretty hard to fuck up because it is supremely delicious!
Those are the foods I can think of that are common to most tribes, but beyond that, every tribe is it's own distinct culture, and each has its own cuisine, some more sophisticated and extensive than others. Mexican and South American cuisines, which tend to be considered some of the richest and most varied in the world, are all based in native cooking, with Spanish, French, and other influences.
Though my mom is Ojibwe, I grew up in Seattle, which meant greater exposure to Pacific Northwest Indian cuisine, which is largely seafood-based (seal, whale, salmon, geoduck, mussels, etc.).