“The guy doing the engraving was probably Clovis ~ which means he had European ancestors who lived in the Western European refugia. They had a thriving art culture.”
Such a scenario is not necessary. Such a scenario posits that different groups of humans living separately and far apart were incapable of acquiring the very same skills and talents. There is no reason to believe that to be the case.
The individual who engraved this piece may well have been an immigrant ~ from Europe!
Before him there really weren't all that many folks wandering around North America.