It's not surprising that a country founded by escapees from European oppression would reject, as President George Washington cautioned, "interweaving our destiny with that of Europe." This was especially true after World War One, an "interweaving" that cost 57,400 American boys their lives and was retrospectively seen as a grievous mistake. Such feelings were bolstered by Senator Gerald Ny's 1934 hearings investigating the armaments industry, which concluded that the US had been manipulated by war profiteers who "paved and greased" the road to battle. The message was obvious for a citizenry caught up in its own personal crises in the Depression: Don't be manipulated again, by anybody.
By 1939, hundreds of American organizations debated America's role in the new European conflict. The majority of them wanted no role at all. Roosevelt seemed to agree, telling parents on the eve of the 1940 election, "Your boys are not going to be sent into any foreign wars." Shortly thereafter, however, and to the isolationists' fury, Roosevelt created Lend/Lease, providing Britain and eventually the Soviet Union with desperately needed munitions and supplies. And he found other ways to support his future allies and circumvent isolationist legislation.
With more than 800,000 members, the most powerful isolationist organization was America First, which included Senator Nye and many other Republicans, and whose most famous member was Charles Lindbergh. America First opposed even "aid short of war." It argued, "American democracy can be preserved only by keeping out," and blamed three groups for enticing America into the conflict. Not the munitions manufacturers this time, but, as Lindbergh said in a famous speech in Des Moines, "the British, the Jewish, and the Roosevelt Administration." "The greatest danger to our country," Lindbergh claimed, "lies in (the Jews') large ownership and influence in our motion pictures, our press, our radio, and our government." Lindbergh's admiration for Germany was well known—he had once called Hitler "a great man" and believed Germany could defeat the U.S. militarily. But the Des Moines speech was an unpleasant revelation for millions of his idolizers.
"We say Good-Bye to Col. Lindbergh, who wants to go and live in Berlin, presumably occupying a house that once belonged to Jews." The New Yorker.
America First disbanded December 11, 1941, just about the time Colonel Lindbergh's first application to join the Army Air Corps was rejected.