> exploration is not exploration if it is not documented or widely known

I'm sure Native Americans had documented their land and made it widely known within their society at the time.

How would they document it? In North America no tribe had writing until after encounters with Europeans. They only had oral tradition, which is helpful for preserving myth and little else.

The history of ancient roads, ceremonial centers, seasonal migrations, and trading along fixed routes by various indigenous peoples would seem to suggest that they had some way of preserving information about the geography. I'm very skeptical that oral tradition is incapable of conveying the lay of the land, in fact, that seems to have been a major function of some of the oral tradition (which describes where other groups of people are found in geographical terms, for example).

It's incapable of conveying anything if the civilization is lost. Maybe the mound builders had an incredible understanding of the land, maybe they didn't, but we can't say they documented it, at least not in any way that's transferable to the future or discoverable by a foreign culture.

Maybe I'm moving the goal posts and I'm not trying to do that, so I'll leave the immediate topic there.