Anti-semitism in US was legal and very strong. Anti-Jew propaganda was everywhere. Ford was one of the most powerful people in US, and he was anti-Jew. Now everything just disappeared. Suddenly Jews control everything.
If anti-Jew Americans were so powerful, why they allowed Jews to take control over US so easily? Why none of the Jewish elite were killed?
2. Whites were susseptable long before jews kicked it into gear. What you're looking back on is an unregulated social space where antisemitism wasn't prohibited. Not a social space where antisemitism was a significant driver of public sentiment. The fact that Ford and Coughlin were taken down - at enormous effort - shows that antisemitism was not popular among white elites. Indeed, British Zionism was more influential than antisemitism.