This is likely insignificant, yet gives some hope. Japan may yet refrain from becoming a pawn, as it would surely be obliterated in a conflict with China. Unfortunately, this is probably but a squabble over blame for imperial incompetence.
Cup half full: either Japan is incompetent or ths US was and is trying to pin the blame on Japan, which will push them away. It could also be a pretext to warn Japan it can be dropped military in an attempt to draw them in, a sort of threat or loyalty test. Either way, imperial disunity favors multipolarity and AES.
You’re probably on to something since the same inter-bourgeoisie clash is occurring in other US-occupied countries, like Germany and South Korea.