Indigenous American oral history can be quite useful indeed at helping us understand precolumbian history, and even post-columbian history. Oral history among indigenous peoples is often the only source we have for their point of view on various events, and likewise often the only reference that exists for 'prehistory' such as the precolumbian period. Although oral history can be often 'tainted' by myth and legend, and can vary regionally even regarding the same story, there is often underlying truth that can be isolated and explored.

If you were to look at the locations of indigenous tribes today, you might never have known the Comanche and Shoshone were originally a single people. Within one orally transmitted story, however, remains a knowledge of the common origin of these two peoples. There is no written history to verify this, no Europeans were present for it, only the aftermath in the 17th and 18th centuries is known when Comanche migrants met and found new plains to roam south and east of their original homeland. The story recounts that a Comanche chief and a Shoshone warrior met at a fresh spring and, in an argument, the Comanche killed the Shoshone, and was himself killed - a period of war followed and the nations split, with the Comanche leaving for greener fields so to speak. It also describes the intervention of a spirit and the creation of one of many Soda Springs. This is our only real account of the separation of Comanche and Shoshone, but that does not mean that truth cannot be found therein - if we remove all supernatural elements, a dispute over ownership of a spring leading to bloody conflict and a separation of the tribes doesn't sound all too improbable.

But that's simple stuff. A more complex case of oral history being the primary informant is that of El Inca, a mestizo descended from Andean royalty on his maternal line, who went on to write The Royal Commentaries of the Incas. This collection of oral history and stories he learned from his relatives in Cuzco, contemporary to the existence of the Inca Empire's rump state and told by people who had lived in a pre-contact Inca Empire, is a first-and-second-hand account of the culture and the empire and its history, and to my knowledge is considered appreciably as a trusted primary source despite being founded most in oral tradition rather than recordkeeping in the European sense.

Several cultures of the American Southeast have oral histories that line up well with modern understandings of precolumbian society. The Mississippian Civilization is understood in some oral histories, and similar to the Comanche, the Chickasaw and Choctaw oral histories dictate a period of time when the two were one before migrating to their current location, splitting into two peoples along the way. Whereas many regions may have appeared to be sparsely populated and disparate when Europeans arrived, their oral histories tell us of a time of great cities, fortified homes, and of trade lanes spanning the continent. It is perhaps no coincidence that stories of trade lanes spanning the continent can be found in other tribes believed to lie on these trade lanes, such as the Karankawa, whose oral tradition told of trade to far-off tribes in the Rocky Mountains, but whose actual experiences with such peoples is hardly to be found anywhere in firsthand writing.

Ultimately, oral histories are a decent source of information regarding the past of otherwise unreported or unwritten nations. This, however, comes with an asterisk: you must analyze them critically. They are fogged by time, by legend, by myth, by changing perspectives. In this way, oral history and 'literature' is much like written history and literature.