Yes, white nationalists are American in the sense that they were born on the American continent, in a nation called the United States. They are entitled to all of the rights granted to U.S. citizens. My broader point, however, is that America is an idea, not a place. America is the idea that people are entitled to a right to enjoy life, acquire and possess property, and to pursue happiness and safety (life, liberty, and the pursuit of happiness). White nationalists do not uphold these values for anyone but themselves, they do not subscribe to the American identity, and so they should not be called Americans.