Japan had a little quarrel with the Russian army in the late 30's which appeared to have put them off a longer conflict with the Soviet Union.
However it would have been more plausible to imagine Zeros flying over SIberia attacking Soviet Prison
Regiments in the snow, than Japan being an ally of the USA.
A possible scenario might have been a pact between Japan and Germany to attack the USSR in 1940 or 1941. And Japan doing all it could to remain neutral with the Americans.
How would that change the war?