Alternate History. What if Japan had NOT attacked Pearl Harbor in WWII?

Japan had a number of aggressive plans for their neck of the woods.  The US did not approve, and eventually embargoed shipment of oil and scrap metal to Japan.  But with Hitler showing us how dangerous Germany was, and isolationism running wild in America, we were not about to do anything to Japan short of diplomatic nasty grams and  embargoes. Had Japan understood this, they could have proceeded to take over places they wanted, like Dutch East Indies oil fields, and more of China.  We would not have gone to war with Japan over this kind of aggression.
   If Pearl Harbor did not happen, we would not have joined the British in the war against Hitler, even if Hitler had the British on the ropes.  Isolationism would have prevented it.  Churchill's entire plan for beating Germany consisted of getting the Americans to help him out.  Without Pearl Harbor, Churchill would have been severely disappointed.
  What's more, if the Nazi's had done some serious diplomatic work on Japan, they might have been able to talk the Japanese into attacking the Russians in the far east.  If this had gone down in the winter of 1941, when Hitler's army was at the outskirts of Moscow, the Russians might have cracked.  As it was, the Russians brought ten divisions back from Siberia and threw them into the battle to save Moscow.  They would not have been able to do that if the Japanese had attacked in the far east.  And the Japanese had memories of the successful (from Japan's viewpoint) Russo Japanese war of 1905.  And the Japanese were still smarting from a sharp defeat the Russians gave them in 1939.  Japan had tried to seize parts of Siberia.  The Russians sent a large army, with plenty of tanks, aircraft and artillery, under Georgi Zhukov, best Russian general of WWII,  and whipped the Japanese thoroughly at a place called Kalkin Gol.
  Any way you see it, Pearl Harbor in our real history, was a key decisive event.