Your broad generalization of American culture is not very accurate. Some people might enjoy this. But usually in a designated place to study or read, such as a coffee shop or a library, starting impromptu concerts can be seen as annoying because it is disrespectful and distracting. That doesn't mean people don't like live music or entertainment. Also, if you are getting your idea of what American culture is based off of reddit or other parts of the internet, your view is going to be very inaccurate. Until you've spent time living in a place, you cannot accurately know what the people there are truly like. And America is very large, and different areas have culture/social norms that can vary by the region. Even as an American I cannot speak on how people feel about stuff in other parts of this large country.