A surprising amount of knowledge has been lost regarding the diet was of various pre-Columbian North American tribes, that is, regarding their diet at the time they first came into contact with European immigrants, and before then, but it is known that diet varied quite a lot from tribe to tribe, and from region to region. General cultural exchange between North American tribes and European immigrant tribes caused significant changes in the diet of the Europeans, and probably caused even more profound changes in the diet of the North American tribes. Efforts to preserve knowledge about the pre-contact diet of the North American tribes, have been rather limited. Nevertheless, some information is available.
According to research published by Donald Treadwell, aka Lone Otter, in My People the Unkechaug: The Story of a Long Island Indian Tribe, Kiva Publishing, Netherlands (originally written as his master's thesis for a master's degree in anthropology), which I found 30 years ago in the local history section of the Mastic-Moriches-Shirley Community Library, in Mastic, NY, all the tribes on Long Island, NY, at the time when Europeans first contacted them, were doing only a little bit of hunting and most of their food was from gathering, and agriculture. Agriculture meant squash, both the seeds and the flesh, as well as corn, and beans. Those were the three main crops, sometimes called "the three sisters." Donald Treadwell debunks the frequently heard story that tribal farmers put dead fish in the soil along with seeds or seedlings that they planted. Gathering meant wild herbs, berries, and clams, mussels, and similar shellfish. Most of their animal source food was from easy-to-get animals like clams, and not from hunted mammals. While it seems that they occasionally hunted deer, it also seems clear, from Donald Treadwell's research, that more often they hunted smaller animals.
Apparently Mr. Treadwell was not himself a vegetarian, and had no axe to grind in regard to claiming that the Unkechaug and other Long Island tribes had a primarily vegetarian diet — almost certainly without any milk or dairy, but quite possibly with some gathered eggs, and of course with the clams I previously mentioned. Clams and other sessile mullosks were easily available in large numbers. Unlike mammals, they didn't run away from people! So you just walked to the sea shore, stuck your hand or a simple tool into the sand, and pulled them out. Despite the easy availability of sessile mullosks, apparently the LI tribes preferred dining on lots of squash and corn and beans. Lots of starch here: some protein in the beans, and both protein and considerable amounts of oil in the squash seeds. They may also have grown melons. And likely they would have eaten the melon seeds.
Where buffalo existed on western plains of North America, tribal hunters hunted the buffalo. How? A popular method was to trick an entire herd of buffalo into jumping off a cliff, causing them to die in huge numbers, slowly, from broken bones. Then the people killed off a small percentage of the buffalo that were lying on the ground with broken spines, and hauled them away. The rest died slowly. Tribal hunters were sometimes very wasteful.
I haven't learned much about the diet of far northern tribes, in what is now Canada and Alaska, nor much about the diet of Central and South American tribes. But the current diet of the present population of Central America seems to be more heavily influenced by the diet of pre-columbian tribes, than the current diet of the present population of North America. In Central and South America, a large segment of the present population, called mestizos in some areas, are descended from both pre-Columbian peoples and European immigrants. In North America, the percentage of the population that is of mixed pre-Columbian, European, and African ancestry, is smaller. It is common practice to identify people who are probably of mixed ancestry as "native American" even though they are only partly descended from pre-Columbian people. People of purely pre-Columbian ancestry are probably quite rare in the United States. In South and Central America the nixtamal that is used to make tortillas has a long history. And it is similar to the hominy that is a staple in the southern states of the United States. However while nixtamal in a common staple food in much of Central America, hominy is a relatively uncommon food in the United States. Such corn products, along with the wide variety of beans available in markets today, and the continuing popularity of squash, is testimony to the fact that pre-columbian diet in many Central American tribes had a lot of similarities to the diet of the tribes of North America's Eastern coast, and of the Appalachian region.
Personally I feel best with a lot of starch in my diet, lots of potatoes for one. Other starches I eat are rice, corn tortillas, whole wheat pitas, whole wheat pasta, caraway rye-bread (made with 2 parts whole grain rye to one part whole grain wheat, and one part refined wheat), quinoa, barley, millet, stone ground oats, and since I moved to the US South, lots of yellow grits. Also, I eat raw and steamed vegetables. I add cold pressed oils to some vegetables (unrefined untoasted sesame oil, extra virgin olive oil), but I don't fry or sautee anything. I eat some legumes and nuts, and oil seeds. And of course I like to keep plenty of fruit on hand. But what I consume in huge quantities are the starchy foods.