Ethnicity is not race. It’s revealed in your accent and your social references and who people think you are if they know your parentage. No one could look at an atheist of Jewish or Christian or Muslim descent and know their ethnicity. At best, they could make guesses about their race and then on that basis guess that, say, someone who looked Middle Eastern might be Muslim instead of Christian or Jewish or Zoroastrian or whatever. The Nazis had to go to a great deal of effort to racialize Jews—even more than Americans had to go to in order to invent whiteness.