On October 11, 1941, the U.S. Navy destroyer USS KEARNEY was torpedoed by a German U-boat and damaged, killing eleven American sailors. Then, on October 31, the USS REUBEN JAMES was torpedoed and sunk with the loss of the lives of over 100 American servicemen. In OTL, the attacks on the KEARNEY and the REUBEN JAMES, while causing much outrage, did not push the USA immediately into war with Germany. But what if?
Let's assume that the torpedo from U-568 which struck the KEARNEY on October 17 sunk the destroyer with the loss of all hands, instead of merely damaging it and killing 11. The outrage over this atrocity is still raging in the USA when news of the sinking of the REUBEN JAMES hits the newspapers on October 31. In less than two weeks, two American naval vessels and well over 200 servicemen have been lost. FDR, sensing that the fury of the American public is great enough to support a declaration of war, goes to Congress, and on November 4, 1941, the United States of America declares war on Germany. Italy declares war on the USA the next day.
What are the effects of this? One possible impact...Japan has not irrevocably committed to the Pearl Harbor operation. With America now on a full war footing and its military forces on high alert, do the Japanese proceed with the plan? If the Japanese cancel the operation, might a negotiated settlement of some sort in the Pacific, allowing the US to focus exclusively on Germany, be possible? Assuming such is the case, how much quicker can Nazi Germany be defeated if all of American resources are focused on Hitler?