The Mein Kampf thread got me thinking.  Hitler was very close to winning the war in Europe in 1940-1941, but a few major blunders/events sealed his fate (invading Russia, Pearl Harbor, Dunkirk, etc.).  Suppose Hitler hits the troops hard at Dunkirk, which would have resulted in massive casualties and large numbers of POW's.   The loss of 300,000+ troops would have destroyed British moral, and would have really put Britain back on their heels.  Subsequently, Hitler could have postponed Barbarossa and carried out Operation Sea Lion (or was it Sea Wolf, can't remember) and pretty much take Britain, arguably within a  few months.   This would have basically given western Europe to the Germans.

So, let's stretch this further.  Suppose Hitler convinces the Japanese to focus their war effort on eastern Russia instead of invading the US.  Russia clearly couldn't fight a two-front war, and would have inevitably fallen.   If this had happened, do you think the US would have stayed out of the war?  Are these even viable scenarios?  

Opinions welcomed!

It is probabable that the US would have stayed out of the war, assuming no attack was made towards American interest at the time.  I personally don't think that the American population really wanted to get involved.  A smart thing Hitler could have done, is perhaps contract comapnies like Lockheed and Boeing to build "commercial" aircraft before the war and continue that project to convice American leaders that nothing bad was happening.

Suppose the Japanese attacked towards Korea/Eastern Russia, and did attack any US held properties/principalities like Guam, Midway, Wake, Somao, etc -  The Japanese would still need to take care of Australia and India in addition to fighting the Russians.  The Japanese power, I believe, was held in the Naval forces - though their infantry was one hell of fighters.  Even then, the fight to Moscow from far eastern Russia is tens of thousands of miles.  And it ain't easy mileage.  For the Japanese to be truly effective - they would have to drive through some hard territory that is hell to take.  

Hitler needed to leave Russia alone - plain and simple.  If he needed the oil resources of the Caucus area - simply invade the middle east.  Nothing but sand and oil there and it was poorly defended.  Build up his army and advance the technologies being developed - then invade with out having to worry about an attack on the western wall of France.

I'd say that no matter how many they lost at Dunkirk, the Brits would not have helplessly let the Nazis invade England.  Remember, before D-Day, large scale amphib operations were tickets to disaster. Hell, Churchill ran the allied invasion of Gallipoli in 1915.  That went so badly, he ended up in a trench in France not long after that. The citizenry in England were supportive of national defense, and while the BEF was a sizeable force it wasn't everything they had.  I've just never seen a viable nazi plan for a cross-channel invasion.  With everything else they had on their plate, I actually doubt the nazis could have diverted enough resources to seriously consider it.

The two front war against the USSR is an interesting one though.. There isn't much of anything but cold out in eastern Russia (Well besides Vladivostok).  One wonders whether the Japanese could have withstood a fighting withdrawl across thousands of miles of scorched taiga, and the Russian winter that would follow.  From what I've seen of the equipment issued to Japanese troops (and what that would indicate about the quality and availability of imaginary japanese arctic fighting gear) there would be fresh japsickles extending a short distance into the interior to this day.  It's possible that misplaced pride could have caused Stalin to squander even more resources in the east though, and that could have provided for a german breakthrough in the west as russian forces were diverted.

Aaaahhh.. "What if?".. The historian's favorite game

I don't think it is a viable senario.   You have to remember that attacking Russia gains very little for Japan other than another front to worry about.  Japanese economic interests lay south.  I think they were also a little suspicious of Hitler's possible long term political control over the French Indochina and the Netherlands East Indies which threatened Japan's transportation routes to China.  Also, of more concern to Japan was the American and British presence as well as the oil fields in the Dutch East Indies.  A non-aggression pact with the Soviet Union was a wise decision on their part.

Unviable scenario because if Germany had invaded GB, the USSR would have invaded Western Europe through Poland and Romania.  The reason that Operation Barbarossa was such a success is because Stalin had his entire strength forward deployed in preparation for invasion as soon as a German assault on GB was underway.  Many historians believe that Operation Sea Lion was simply a strategic deception intended to do exactly what it did.  I've read that the Soviets actually noted and were alarmed by German preparations along their border and were assured that the build up was simply an attempt to decieve the British.  The Germans HAD to invade the USSR - they were existential enemies and both couldn't survive.  When people say the Germans made a mistake invading the USSR they fail to take into account that Communism was not a peaceful doctrine.  Look at Soviet actions in Spain, Hungary, Finland, the Baltic States, Eastern Poland.  Stalin was every bit as brutal and expansionist as Hitler.  The German invasion of the USSR was entirely necessary to eliminate the threat, not just to Germany, but to all of Europe.

The actions of the Japanese and their relationship with the USSR is interesting.  The two countries had a nonaggression treaty and maintained an active trading relationship until the day after the Bomb was dropped on Hiroshima and the USSR invaded Manchuria and the Kurile Islands.  Most Americans don't realize to this day that, while we were supporting the USSR through Lend-Lease, the USSR was trading raw materials like coal, lumber, grain, iron, leather to the Japanese.  Of course, by that point FDR had our government so filled with Communist spies that NOTHING bad about the USSR was allowed to come out.