The Chinese at the time were mostly not communists who were fighting and dying. China did tie down a vast amount of Japanese infantry, but I don't think it's fair to discount the United States' role in actually fighting and doing heavy lifting (I should correct though, China did too) in the Eastern front. The Western front without the US would have been even bloodier but it looks like the Soviets would have eked out a win. I don't think that's the case at all in the East without the United States.