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.
It's the symptom of being imperial periphery. What you see is the conflict between national bourgeoisie and the comprador bourgeoisie.
You're probably on to something since the same inter-bourgeoisie clash is occurring in other US-occupied countries, like Germany and South Korea.