Click to enlarge.
Disney animated features mapped out by geographical location.
For The Little Mermaid, I couldn’t find any definitive proof as to where it takes place. It came down to Denmark or the Caribbean. Basically 50/50, there were signs pointing to both and also negatives. I chose the location I felt best represented the film as I’ve seen it. I don’t doubt that many think it’s wrong. But, I bet had I put it in Denmark there’d be issues with that as well.
For Atlantis, well, that’s a pretty obvious case of no one knows where Atlantis is located. The movie (to my knowledge) never explicitly states where it is, so I went with the prevailing theory behind it’s disappearance. Honestly though, I could have put it anywhere on the map and it would have been “wrong”.