What is the culture that some Americans try to preserve?

Just because we want people to come legally and respect our rules means we are scared of loosing our culture? What part of multi culture do people still not understand? Usa has many cultures but all hold on to the same belief.. The American flag, rules, morals, speaking english and American holidays. If you dont respect these things then you dont belong here. And if I have to explain this one more time to someone, Ill kill myself..