Plato made the mistake of calling the continent of Atlantis an island or this was a mistake in translation. North America really was the Continent of Atlantis. Here is his quote:
“and there was an island situated in front of the straits which are by you called the Pillars of Heracles; the island was larger than Libya and Asia put together, and was the way to other islands,”
See the continent on the map. https://goo.gl/maps/JyjYjaygJYK2
The island of Atlantis was much smaller.