In geopolitical game, it is the same as social status game. There is big country syndrome and there is inferiority complex small country syndrome. The big country like USA, China, and Russia are in a different league and they don't regard smaller states as equal even though for political correctness, they strive for equality. The US can said whatever they want. They publicly support Japan military buildup but secretly scare the living shit out of them that they will lose their prestige status in Asia, as Japan's puppet master. This is why the US will never allow Japan to build up. They will allow small build up but not a complete build up because they know they can't put a tight lease on Japan. Japan, on the other hand, don't have the ball to face us one on one and depend on the US for protection. If they build up, they rid alienating the US and the US will abandon them. This is why the current relationship between US-Japan is at a dead lock. Both want to increase military relation but both have a different idea of what exactly is an appropriate buildup.
We win regardless. If US push us too hard, Sino-Russia's East alliance will grow stronger. Our fate is decided by ourselves. We already declared a military arm race with Japan. We want Japan to choose a hard path, either face alienating the US or accept our supreme dominance on the Asia continent. There is no way Japan can keep up with us. We are talking about now. In the future, we will grow too powerful to be contain.