No, they possess nuclear weapons as a bargaining chip to get more welfare. That and they cannot really afford to maintain the massive conventional forces they have, all those soldiers and artillery pieces cost a fortune to maintain, nuclear weapons are relatively cheap as a deterrent.
Seems like you want to blame Americans for problems that began well before we even showed up. The east is like the middle east, they have been fighting each other for thousands of years, westerners are late to the party, blaming them is foolish.
What little military capacity Japan currently has is dwarfed by both china and N. Korea, the N. Koreans have a million man standing army in addition to their nuclear arsenal.