What if America ALLIED with the Germans in the 1930’s?

I think that the whole system of alliance would change. The fact that Germany and America had suddenly become all chummy would not alter the fact that Japan and the USA had massive economic and territorial rivalries in the Asia pacific region. In the end we would likely see Japan simply dropping its entirely useless alliance with Germany and joining the British Empire and USSR. Japan would be especially enthusiastic to do so, picking off britain's possessions and having a large enemy in her Imperial possessions and the ANZACS was never beneficial to Japan herself. Relieved of guarding her Manchurian border against the USSR's crack Siberian contingents, Japan could comfortably concentrate on pursuing her control of China, the Phillipines and the American Pacific.

So Britain, Australia, New Zealand, Canada, Britain's Empire, Japan, France and her colonies (if they hold off the German onslaught) and the USSR would be mobilzed against the Axis and the USA. I don't want to go into the likely course of the war right at the moment, suffice to say I think the US/German alliance is doomed to fail in the long term.