I think this speaks mostly to the kinds of people you have interacted with in the USA. White teeth are very much a status symbol since you have to be at least upper middle class to have them, so people go out of their way to have teeth whitening procedures done as sign of high social status. But if you went on a tour through an amazon packing plant you’d see a lot of people with missing or crooked or yellow teeth. Our working class is almost invisible; if you’re well off you might not interact with them much at all, but they exist.