For more context, the fascists in Japan are mad that Trump said that China was allied with the US during WWII because the fascists in Japan believe that KMT = China. The fascists in Japan are saying that the US allied with KMT during WWII and not PRC. Fascists in Japan are asserting that Taiwan is the "real" China.

China was indeed an American ally during the war against Imperial Japan. But the China that the U.S. partnered with back then was the Republic of China (ROC), ruled by the Kuomintang (KMT), which later fled to Taiwan.

The narrative of the Chinese Communist Party, however, is that it led the "liberation" of China, claiming full credit.

https://archive.is/aNTYC (nikkei japanese news agency, nikkei also owns 'financial times' FT )

I think maybe Japan fascists are trying to draw attention away from which side Japan was on in WWII.