These maps represent what Americans are first taught about the world as children.
For a majority of Americans (speaking as an American now overseas) these maps are maps about feelings, rather than about knowledge.
It’s true that there are some Americans who never progress beyond this viewpoint, but the majority of American adults are not quite this uneducated. Among those who are, it comes from the “We’re number one!” mentality that pervades what children are taught about America (or at least were until recently).
No matter how knowledgeable we become, it’s true that we can look at maps like this and understand the reasons they are drawn that way immediately–from our first knowledge as children. That’s what makes them cartoons, that some of those feelings stay with us forever, in spite of our knowledge.