How the United States might enter the war without Pearl Harbor

If Japan made peace and Pearl Harbor never occurred, how might the United States enter the European war?

The likeliest route would be expanding Atlantic neutrality patrols that eventually caused an incident or prompted Hitler to declare war; a voluntary U.S. declaration against Germany would remain politically difficult.

Roosevelt would have had little chance of obtaining a direct declaration of war on Germany without a German move, while American neutrality patrols could spread steadily farther across the Atlantic. That expansion might create an armed incident or provoke Hitler, who could treat the patrols as a de facto act of war and declare war himself. A longer period outside the conflict would also change Allied resource allocation: Britain could draw on North American production while spending less effort building infrastructure for arriving U.S. forces, potentially accelerating radar, interception, and long-range bombing projects aimed at German oil. U.S. deployment brought substantial military value, but hosting it also required British engineering and logistical resources.