You have not done enough reading. https://tinyurl.com/yakxdmbl
I am well aware that there was migration to the Americas before the land bridge migration. This link doesnt claim there were massive cities 20000 years ago though.
It shows you that there were people here tens of thousands of years ago and that they were negros. Which is completely contradictory to mainstream history. There's more links google em
Interesting change of topic. Yes I know there is evidence of African, and Australian aboriginal migration to South America. You confuse grade school history with mainstream history.
Doesn't matter what you call it really. The official story line of transatlantic slave trade etc. is a lie. It was created to support European colonialism Not sure how thats mainstream