[mad=dog]

Well the peculiar thing is that the Axis was not a true alliance. Japan didn't declare war on Russia either remember. They were not obliged to as Germany attacked first.
Germany declared war on their own accord and faced the consequences. Perhaps Hitler was swayed by the reasonable initial sinkings from u-boats into thinking that transport of troops across the Atlantic impossible. Naturally he was wrong.

The Axis was poor at coordinating their efforts. The Germans had excellent naval radar, but the Japanese had none! All those mighty ships and they were dependable on visual ranging equipment. Since we are playing with history one could also ask how things had fared if the Japanese capital ships had radar systems of similar quality to Bismark.