Multiculturalism is an invitation for a divided society. It's fine to be proud of a person's culture, but to come here they left it. We have an American culture and people need to assimilate into it. Learn the language and traditions of their host nation, otherwise will cause them to be isolated from the greater (larger) society. Look how multiculturalism and isolation has worked in Europe (France, Belgium, Germany, anyone?).
America always was a "melting pot" where we all become one people. Multiculturalism is contrary to that ideal. If we have a thousand different cultures (societies), we become a fractured nation and turmoil can, and will, eventually ensue.
People should come to America to be Americans.