Huntington was not making an argument for an Anglo-Protestant understanding of American identity if that meant that only Anglo-Saxon Protestants could qualify as Americans. Rather, he was saying that the Anglo-Protestant settlers to the United States brought with them a culture that was critical for the subsequent development of the country as a successful democracy. The culture is important, not the ethnic or religious identities of those who take part in it. His view is, in my opinion, undeniably true.
