People keep swallowing even the most implausible intelligence lies. From Ron Unz at unz.com:

Historical Examples
During 1940 the determined efforts of President Franklin Roosevelt to involve America in the war against Hitler’s Germany were blocked by the overwhelming opposition of the American people, running at 80% according to some polls. A group of young Yale Law School peace activists had launched the America First Committee and it quickly attracted 800,000 members, becoming the largest grassroots political organization in our national history. The leadership of the AFC included many of our most prominent business and journalistic figures, and famed aviator Charles Lindbergh, one of our greatest national heroes, served as its top spokesman.
With American antiwar sentiment so seemingly strong and resolute, various political stratagems were employed to reduce it. In late October 1941, just few weeks before the attack on Pearl Harbor finally settled the issue, FDR announced in a nationwide radio broadcast that he had obtained a German map that revealed the secret Nazi plans to seize control of Latin America, which Hitler would then use as a base to attack the United States as part of his bold plan of world conquest.