Vikings.
I read somewhere (long before the internet) that some ancient Viking (Scandinavian?) artifacts had supposedly been found in Arizona or New Mexico.
Local tribes there have legends of their ancestors battling red haired giants.
Perhaps some of Leif Erikson's crew that stayed behind and worked their way West.
On the eastern edge of Oklahoma are well preserved Viking tracks. I think a state park is built around the site. Near Poteau?
There is a great video on youtube about the collapse of viking colonization of Greenland speculatively caused by the coming of the little Ice Age and Plague cutting off their re-supply from Norway and Denmark.
There is speculation that as the inhabitants fled Greenland they traveled west instead of returning to Scandinavia. This would explain Viking artifacts found in various North American locations.
Seems like a plausible theory to me.
SC, pinged you because I thought you might like the video.
The Greenland Vikings - Land of the Midnight Sun
https://www.youtube.com/watch?v=lmbY-GrM8pI&ab_channel=FallofCivilizations