The argument that America even has a singular culture to preserve is, I think, a false premise. America is multi-cultural. There are American _ideals_ which can be preserved ("life, liberty, and the pursuit of happiness"), but the country is too big and too varied for anyone to claim that there is a specific American culture, or that there has been since its founding.

America is Indian, Mexican, and Muslim. Not "them", but "us". Maybe some Trump supporters disagree?