China's contribution to the Asia-Pacific war is forgotten in the US because it was politically embarrassing to FDR's legacy and to his political heirs. During the war Communist disinformation fueled anti-Chiang propaganda. After Mao came to power, the Truman administration found it useful to emphasize Chiang's corruption and incompetence in order to escape the blame for "losing China".
China Lost 14 Million People in World War II. Why Is This Forgotten?
When looking back at World War II, the victors see their own military contributions the clearest. Hence the United Kingdom spotlights the Battle of Britain and El Alamein, the Russians Stalingrad and Kursk, and the Americans D-Day and Midway. The contribution of China, whose war was the longest and among the bloodiest, tends to be forgotten in the West, and for years was little commemorated even in China.
A new book, Forgotten Ally: China's World War II, 1937-1945, by Oxford historian Rana Mitter, aims to sharpen this fuzzy picture by presenting the Middle Kingdom’s eight-year war against an invading Japana war that had been under way more than two years before the Nazis invaded Poland, which is the usual starting point for histories of World War II. “Essentially,” Mitter explained in an interview with Pacific Standard, “the politics of the Cold War covered over that what is coming to be realized, I think, as one of the great missing pieces of the jigsaw puzzle of World War II.” Now, however, a combination of archives in China opening up and a new political attitude by its leaders has cracked the historical window....
While the Nationalist leader Chiang Kai-shek and Communist Mao Zedong are usually depicted as the titans of China’s resistance and its on-again, off-again civil war, Mitter details the rise and eclipse of a third figure, Wang Jingwei, whose stature and influence long equaled Chiang and Mao’suntil he made accommodation with the Japanese.
The scale of China’s involvement in the war was massive. Chiang, for example, fielded four million troops at the Nationalist’s height, while China as a whole lost an estimated 14 million in the war. Had China folded, Japan’s capacity to fight the U.S. or even the Soviets would have been vastly amplified.
The '"progressive" narrative gave the credit for Chinese resistance to Mao and his "agrarian reformers” while blaming Chiang for every short-coming of the Nationalist army and economy.
It is only in this century that a few intrepid historians have presented a more accurate picture.