I find that very unlikely. If it is true please don't go around making statements like we are taught in america is that nothing happens outside of america.
You can't speak for America as a whole since we don't have a national curriculum.
More than likely you just feel the way you do because you just took US history and haven't gotten to any or the world history classes.
>We're taught as if there is a concrete separation between American History and World History,
There's nothing wrong with teaching a separate US history and world History class. When you get to college you'll find that history classes are even further subdivided by time and geography.