A lot of these flyover country bigots you speak of have no clue who is part of the Jewish faith and who is not. Most American Jews do not have accents or wear religious garb that would make them stand out, as may have been the case in the world portrayed in Portnoy's Dilemma based in 1920s New York City. Post-WWII, many of those that immigrated to the United States are of European heritage (Polish, Italian, Ukrainian, Russian). In fact, there is a long tradition of efforts (pre-WWII) made by American Jews to force immigrants to hide their Jewish roots and cultural traditions to "help" them avoid the kind of discrimination faced by other European groups (Irish, Italians) by the majority culture. There is an excellent article delving into the history of Jewish perceptions in the US in the magazine Jewish Currents:

https://jewishcurrents.org/our-white-supremacy-problem