Well if all that counts is who's fighting >= 51% of the Axis, then you have to take into consideration that the USSR didn't even join the Asian theater until the day after Hiroshima happened despite sharing a border with Imperial Japan and having struggled through a brutal war of attrition with the Japanese just a couple decades earlier.

This idea you and many other armchair historians have that the USSR can solo 1v1 the axis powers and win isn't any less naive than saying America saved Europe, because it ignores the significant amounts of foreign aid that the US donated to other allied nations. This includes the USSR, who would not have been able to carry out a successful war of attrition against the Germans without a consistent pipeline of supplies and weapons. It certainly would not have been able to win a war on two fronts if the Japanese felt free to invade the soviet far east. I will concede that the Chinese deserve way more credit than they generally get for waging their own war of attrition against the Japanese which prevented them from going to war in the soviet far east, but that was also made possible with significant American logistical support.

But more importantly, you seem to have an oddly eurocentric view of history in which the european theater is the only one of any import. Japan's eventual defeat was never a foregone conclusion, and they were just as cruel to their conquered foes as the Germans were. They were also the only Axis that posed a credible threat to the United States, having successfully established a foothold in the Aleutian Islands with an aim towards invading Canada and the United States. Realistically I don't think it ever would have worked (again, they were pre-occupied with China) but they certainly have a better track record of attacking the North American continent than the krauts ever did.