[SunkenCiv]

The only (surviving, known) ancient source for the Atlantis story is Plato, and one of the details that suggests inside info of some sort is the remark that, west of Atlantis, one would have found islands, and following those, one would come to the land that could most truly be called a continent -- the Americas.

[Cronos]

It seems obvious to me that Atlantis was North and South America.

And why "obviously"? I would mostly discount the entire Atlantis legend as, even if there is a grain of truth in it, Plato mythologized it to such a great extent, it's not really true any more. It may have been a small village that was drowned under the sea or it may have been more. Plato is not a satisfactory source to declare that Atlantis did ever exist at all.