Culture exports carry with them morals, ethics, and value systems. Different countries have different m/e/v, and they may not want America's. There's nothing to say America has the right set of m/e/v; hell, people bitch about America's puritanical nature on this very website all the time. In which case it's easy to see why a country might be concerned about importing America's culture, given the m/e/v that come with it.