You're assuming Atlantis existed. Possible that word got back to the Greeks(which is our main source) of North America, but it would have been through northern island hopping or the land bridge, most likely the latter, not by crossing the Atlantic. And there most certainly was not an advanced civilization here thousands of years ago. There would be evidence of that, and there isn't. As for earlier settlers who either died off or blended in with what we now call first nations, possible. But again, there isn't very much strong evidence to suggest that. Not that I've heard about anyways.