Firstly, completely dismissing Japan as a sovereign state. Complete disrespect.
Secondly, nuclear warfare is the dumbest solution possible. Who ever fires first must accept potentially losing the trust of all nations. No matter who fires for whatever reason. Barring an alien attack or something of that magnitide.
Thirdly, the US power does not come from its military - but diplomacy. Allies in strategic places captured by the flow of capital. The military maintains the status quo but isn't invincible. If it were, Russia would not exist. China would not become a superpower.
These are basics.
Having a critical view of the world is a great thing, and I can only commend you for that. But you need to look into the facts first.
In the case of Japan and South Korea, those are not sovereign states but protectorates of the US. At least because they were occupied by the US post WWII and limited military autonomy because of US directives.
My point being the US is an imperial state masquarading as a cheerleader of democracy. The only reason no one says anything is because the US has the biggest stick in the room and anyone refusing to bend over to be shafted is public enemy number 1 ie. China, Russia and the levant.
Its surprising how weak Europe is considering how much experience they have in warfare but it is what it is.
This is completely different from the mutual defense agreement that Japan has with the USA, where it has been made very clear that the USA will protect Japan.
I understand you want to have a critical opinion, but you need to look at the facts.