During the fall of 1941 (but before December), the United States waged a "war short of war" against Nazi Germany's submarines using escort vessels, the Reuben James, the (James) Greer, and the Kearny that was operating in "waters necessary to the defense of the United States," that is, all the way out to Iceland (according to President Roosevelt's definition). They were protecting convoys of British and Canadian transport ships.
The Lend Lease Act of 1941 gave Roosevelt the right to lend or lease military equipment "vital to the defense of the United States."
Could America have taken this to its logical conclusion and escorted British supply ships all the way to Britain, or even Russia, or better yet, shipped arms to them in American vessels? This would be to force the Germans to either "lay off" American ships, or else risk war with the United States by sinking them.