This is not only an American problem. Most people in most countries get their view of the rest of the world from mass media and social media. In some places people think particular groups they meet or read about (e.g. tourists or workers) are typical of the country they come from.

Travel produces different distortions. A lot of British people think the rest of the world is a lot better than it is because they visit places on holiday: they visit nice places and have good experiences. I have known some to get into messes when they actually try to live somewhere else.