The fact is the Chinese Army was too ineffective to defeat the Japanese. As I understand it the main offensive plan was to have US B-29's bomb Japan into submission. But once we had the Marianas bases they were much more advantageous than the Chinese bases. The Allies were not able to open a major Chinese port for supply before the end of the war.
Chaing might have been able to pull it off, but neither he nor the US anticipated the boost the Red Army would give the Communists by turning over land and equipment seized from the Japanese in Manchuria during the last days of the war. As planned in the Teheran Conference.
Gee I wonder why Stalin was so eager turn on Japan after the defeat of Germany.