America's Fight Over World War II, 1939 - 1941 (2013)
FDR invited Lindbergh to the White House in April, 1939, to "get his measure" of the only other American that equalled him in fame, and also to try and find out how much of a problem Lindbergh would be in the upcoming trouble-filled months. Lindbergh thought the meeting went well, and the Air Corps Mail controversy was in the past, but he knew that whatever "Honeymoon" that existed between him and President Roosevelt would probably not last very long.
The shock of the Nazi blitzkrieg convinced many citizens that American military involvement in the war was very near. The national debate centered on this question: Should the U.S. aid Britain, and should the U.S. go further and enter the War in Europe? For the next 2+ years, that debate raged across America: should the U.S. be an Isolationist "Fortress" Nation, with a strong navy & air corps to defend itself (the Treaty of Versailles buttressed that perspective). Or, should the U.S. be an Internationalist Nation; that point of view held that the times were far too dire in Europe for the U.S. to avoid getting directly involved. To an Internationalist, Britain's existence was vital for America's security, and the U.S. had a moral obligation to stop the evil of Adolf Hitler; that view was challenged to the "nth degree" by the Isolationists.
FDR convinced himself that Lindbergh and the "Firsters" posed a major threat to the U.S.; FDR embarked on a dirty, nasty campaign to destroy the influence / reputation of the America First Committee, and especially the reputation of Lindbergh. FDR authorized FBI investigations on Lindbergh and many other "Firsters", as well as publicly labeling Lindbergh (& the "Firsters") as subversives, or even Nazis. Lindbergh and America First portrayed FDR as a dictator who had destroyed free speech in his "Rush to War". . . Lindbergh went so far to say that Democracy no longer existed in America. (Theodor Geisel, also known as Dr. Seuss, was not only an author of children's books, but also a political cartoonist for PM, a New York City Internationalist newspaper. His political cartoons skewered Axis leaders and American Isolationists before Pearl Harbor)
(Below: Lynne Olson comments on FDR and Lindbergh before Pearl Harbor)