But the we would be at war with Japan as it happened on Dec 7th. I would suspect a sizable majority would have supported increased measures against Germany for the sub threat off of N America.
If Germany didnt declare war on us, then the war in the Atlantic would have been quite a political and military minefield.
Syscom...
With regard to the first paragraph, I do not think such thing was a likely event. How come?
Easy. During 1939/40/41 U-boats operated under severe restrictions and directions issued by the High Command. Hitler was deeply concerned U-boat operations in the Atlantic could be seen in Washington as a direct threat to U.S. shipping; Dönitz issued directions to U-boat commanders accordingly.
That a U.S. vessel would be misidentified by some skipper then torpedoed was the primal fear; such restrictions implied a tremendous headache for U-boat commanders due to the complexity of conditions confronted when patrolling the seas, especially at night or poor weather. There would be times when proper identification of the vessel was nearly impossible.
Sound evidence to support and substantiate the assertion lies on the fact a large number of merchant vessels were first intercepted by the U-boat, a German party conducted boarding of the ship to review papers and cargo, and if the vessel was from a non-combatant, the Germans let her continue sailing.
All in all, the Germans did everything possible to avoid hitting any U.S. vessel during the first two years of the war. On the contrary, the U.S. had been involved in convy escort tasks, and also harassed some U-boats until the USS Reuben James was sent to the bottom by U-552 -under Erich Topp-.
Utter rubbish to officially declare yourself neutral while embarking on escorting vessels that belong to one side that is the enemy of another in times of war.
So if the U.S. remains neutral and political manouvering in order to gain congress support for war in Europe becomes impossible for Nice Grandpa Roosevelt, and keeping in mind U-boat policies in the Atlantic to avoid frictions with the U.S.A., i do not think the USA messes with U-boats.
If the oil supply for Great Britain becomes partially or completely severed due to Japanese action in the Far East, then oil from different regions must be found...where? Caribbean Sea...U-boats proceed onto the area, so the Royal Navy would have a new -CRITICAL- sector to protect with its very own resources.
Atlantic, Mediterranean, Indian Ocean plus Caribbean...seems well beyond the potential of the Royal Navy.