[RoaldLarsen]

As I recall, the US didn't enter the war until after it had been running 2 1/4 years. IIRC, they only joined the hostilities when somebody made the mistake of sinking some of their battleships in a sneak attack without prior declaration of war. Who knows how long it would have taken them to join the just cause if potential enemies had just left American ships alone.

The cold war might have been a very different thing if the US had entered the war before the fall of France and more than a year before the German invasion of Russia.

At a guess, the Germans would not have invaded Russia, the Russians would have attacked (for which they were building their armed forces.) The Eastern front at the end of 1941 would have been 1,000km further west than it actually was. Italy would have been knocked out of the war sooner, and there is a chance that Spain might have been invaded by the Allies. Unless there was a separate peace with the Western Allies, it is unlikely that the Russians would have been stopped before they hit the Rhine, and possibly not until they hit the Atlantic.

The Western Allies had a hard enough time defeating a fraction of the depleted German Army. Could they have beaten the Army that defeated Germany? I doubt it. So they probably don't fight Russia straight off, and all Western mainland Europe becomes Communist.

Tough call on how this would have affected the Japanese. With the US involved in Europe they seem to have a free hand to act in the Pacific. OTOH, with Russia not nearly so close to disaster, they would have felt less confident about China. My guess is Pearl Harbour might have come a bit earlier, if they could get the units ready, but the Brits would be trying to avoid a war between Japan and the US so as to bring Japan in against Russia. Then the cold war gets replaced by an earlier shooting war, with the West, Japan, India, Turkey and one Chinese faction taking on Russia and another Chinese faction.

Would have made the actual Second World War look like a sideshow. I think you should have taken the shot. Are you willing to accept that responsibility?