Avi is right. If you look at the statements of Jewish leaders during the war, that’s exactly what they heard from the US government. In fact, a lot of his enemies tried to spread the rumor that FDR was a Jew, using the similarity of his Dutch name to Jewish ones. Google Father Coughllin and his anti-Semitic radio show for a sample.
And to quote someone I knew years ago, a non-Jew from a previous generation: “Jews are OK, they’re almost as good as white people.” No, we aren’t “white,” and plenty of “white” people still think we’re a different race and believe that Rothschild, or Soros, or some other fictional conspiracy, are actually running the country from behind the scenes. Some things don’t change. The world was horrified by what they learned about the camps, but there’s a new generation of non-Jews who don’t remember, and the Holocaust-deniers are flourishing.