I don't think the relationship between us and japan is that sweet as it appears. There is no real friendship in politics, today's friend may very probably kick your ass someday in future, only if it can get more benefit from kicking your ass than being friend with you. I think the japanese people are still holding great hatred against us but they just hind it in their mind, the us would be their first target to with if they got that power. russia/china use N.K. as the fence of their houses while the us also treats the japan just as a pawn to prevent them from expanding their affaction to the Pacific Ocean. I think us would rather to let N.K. have nuclear weapon than japan, though japan is a very "loyal" ally with us.
politics is more complicated than whatever we can imagine so the politicians consist of only the smartest people, espeically the international politics. Hillary Cliton is obviously not capable enough to work as SOS, that's why I have been ranting that Obama should have given this job to Halle Berry who is the smartest woman of the world.