Earthworks
Prehistoric Earthworks Travel Suggestions
The eastern U.S. has several prehistoric earthwork sites. Unlike the megaliths of Europe and East Asia, these become overgrown with vegetation and their once-distinct shapes fade. But once you appreciate what they are, they can become quite impressive.
Nonsensical pseudoarchaeology is deeply racist. It insists that non-European cultures were all "too primitive" to have done anything. They must have been helped by extraterrestrials, or widely wandering Egyptians, Phoenicians, and so on.