Well, a few clarifications on Roddoss' original proposition are necessary;

Does Germany still persue the U-boat war well into the Atlantic or do they limit their operations to just waters close to the British isles?

Does the US still allow Britain, Russia, etc., to buy arms and munitions from them as they originally did?

Is Lend-Lease still in effect? Much of the early protion of this program was geared more to enhancing US "hemisphere defense" than to particularly giving away munitions for a song so to speak?

Does the US continue to supply arms to China?

Does the US continue embargos on critical materials to Japan? If not, why? After all, the US position was more about an aggressive Japan and that is still occuring if Japan attacks the Soviet Union. Just placating the US over China is unlikely to bring much relief if the Japanese attack Russia instead.

Does the US continue to ramp up its own military programs as they historically were doing since about 1938?

Do the Japanese get involved in a conflict with Britain, et. al., in the Pacific as well? Or, are they limiting operations to Russia? If the later how do they handle the embargo of rubber and manganese coming out of Malaysia when Britian (without doubt) cuts it off crippling their economy?
Japan can survive with US oil and none from the DEI or with oil from the DEI and not the US but if both are cut off where do they get their oil from?

If the Germans do manage to push the British out of much of North Africa what happens when they start running into US interests in the region regarding oil and ports / shipping like the Suez Canal?