North America / South America colonized by the Nephilim after being driven out of the Promised Land by the Israelites. They took Mongolian slaves with them, these became native Americans.
Darn right the Lord GOD sealed off both continents, they were HQ central for Satanic Worship and Human Sacrifice.
Smallpox and the Spanish wiped out those cultures, and good riddance. The so-called Plains Indians on horseback culture succeeded this as Horses were not in North American until the Spanish came.
None of this is in the history books, of course.