Although they could have been obtained through round about trade with other tribes, and moved hand to hand over thousands of miles, they could also have been made easily by Maya then invading the South Central states.
BTW, that's a KNOWN FACT. Culturally Mayan people were present in North America, and certainly South Florida and Caribbean islands.
The Mayan civilization dominated the region in and around the Yucatán Peninsula of what is now Mexico. Since Mexico is in North America, I’d say that fact has been known for about, oh, 500 years.
Brasstown bald Mountain is near Lumpkin County, GA which was the epicenter of the gold rush of 1830’s. Same Gold rush that caused Andrew Jackson to rescind all native claims to lands and auction all lands off to pioneer settlers so as to eliminate ‘foreign’ native interests. Same goold rush that led to the trail of tears. The Maya and Aztecs had a thing for gold.
Weren't those built by the Adena tribe? I don't think they had anything to do with the Mayans, who would (IMO) left something more complex than a mount of dirt.