Bringing religion into this- When people started to build the Tower of Babel, they thought they could reach heaven. God got mad at them and spread the people making it all over the world. He also changed their native languages, so they could not possibly build another Tower of Babel. Thus Native Americans in North America before the Europeans came and conquered them.
It's in the Bible
Actually part of my theory states Noah's account of traversing the flooded world in search for land could depict the Jewish peoples' flight from Atlantis to a new land.And an even further extension on this portion states that Babel itself was either Atlantis or a major structure in it that was never completed.
One question:Why would an entire city sink?