Do not fret my friend, nobody is trying to wipe out our culture/heritage/ancestry. Our nation is a culture of cultures. Like everything in life, it is transient and evolves over time. Colonialism gave way to the Victorian era. The Victorian era to the industrial age. The industrial age to the nuclear family. The nuclear family to the hippies. And the hippies (confoundingly) to the information age. Etc.
The impact, importance, and history of our culture/heritage/ancestry is well preserved. In our books. In our films. And within each of us. Immigrants have shaped and changed our identity throughout the entire existence of the United States through a process of Hellenization. We extract the best parts - and jettison the rest. For multiculturalism doesn't mean equal value. But rather equal consideration.
We have much to be proud of. Not as nationalists nor supremacists but as Americans. Because we don't just tolerate other cultures. We celebrate the best of in each of them.