By contemporary standards, America in the first half of the 20th century was a profoundly racist nation. Jews and people of color were openly barred from clubs, colleges, neighborhoods, and mainstream American life. In vaudeville, racist humor dominated. Performers playing African Americans were required to appear in blackface, while stage Jews had to wear long beards, and be venal Shylocks.
By 1939, the anti-Semites had two causes: keeping America out of the European war, and keeping European Jews out of America. And they had two famous men in their ranks. Henry Ford was a true rags-to-riches hero. He was also an anti-Semite, who railed incessantly against "the Jewish plan to control the world" in his newspaper, the Dearborn Independent (circulation allegedly 700,000), which Ford dealerships distributed free of charge. A collection of Ford's ghostwritten columns was published as The International Jew: The World's Foremost Problem — a best-seller in Germany.
The other famous American was Charles Lindbergh, who may have been an anti-Semite, but most certainly claimed publicly that Jews were trying, partly through their ownership of the media, to draw America into the war. Lindbergh represented America First, the powerful isolationist organization that, in fact, ejected Henry Ford for his anti-Semitic views. (See The Isolationist Movement.)
Also ejected by America First was radio preacher Charles Coughlin of the Christian Front, an underground army that attacked Jews in the streets of New York and elsewhere. Coughlin's allies included the German American Bund, led by Fritz Kuhn. ("I will become America's Hitler".) The Nazi-sympathizing Bund had elaborate summer camps and held an infamous 1939 New York rally attended by 20,000 people. Some Bund rallies were enthusiastically broken up by gangster Meyer Lansky and his boys, while Minnesota gambler David Berman was so effective disrupting rallies of the anti-Semitic Silver Shirts that the Silver Shirts stopped holding rallies.
The most powerful American anti-Semite was practically unknown. Breckinridge Long, who claimed to be under persistent attack from "Jewish agitators (who) all hate me", was a former ambassador to Italy and great admirer of Mussolini. As the U.S. State Department's man in charge of helping Europe's Jews, he deliberately created bureaucratic obstacles for refugees seeking visas, and found ways to block many humanitarian efforts. 90% of the immigration quotas from countries controlled by Germany and Italy were therefore never filled. Had they been, it's estimated that the lives of 200,000 people could have been saved.