Other forms: nativisms
People who oppose immigration because they feel their culture will be lost or blended in with a new one can be said to believe in nativism.
There have been times in history that nativism allowed a culture to survive, particularly Native American Indian tribes. When the dominant group practices nativism, however, the result looks a lot like a hatred or fear of people who look different, speak a different language, and hold different beliefs than the majority of people.