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.
The US is drowning, and trying to pull as many of their allies under with them. The smarter ones are trying to avoid that, the dumber ones are rushing headlong into the water.