Kissinger's religion was 'Jewish' (Judaism). The person 'Kissinger' was a German by birth. Just like Albert Einstein. (German physicist, U.S. citizen from 1940)Jew is an ETHNICITY as well as religion. The overwhelming majority of European Ashkenazi Jews even though they lived in europe for a couple of millenia, are distinct genetically from the Europeans, Russians, Germans, Poles, etc. For centuries they lived apart, in their own isolated communities and they share a certain ethnic heritage, not just the cultural/religious heritage. There was very little intermarriage until the last 19th century.
And less than half the Jews in Israel are Ashkenazi.. Juadaism is a religion, it accepts and embraces converts. Israel has immigrated thousands of Somali Black African Jews and others from around the world. Ashkenazi Jews are just one subsection, like Irish Catholics.