There's nothing inherently wrong with nationalism, its the scapegoating often inserted by politicians thats dangerous.
Nail on the head.
Japan's form of nationalism was absolutely insane. I think it's a remote threat at best (worst).
They know that this kind of rhetoric can bring the US into the debate. That way, Japanese leftists whose ideology comitts them to telling that Japanese nationalists nationalists to shut up can instead just sit on their hands while noisy Americans do their work for them.
The US can profit from a well-armed and confident Japan against CHINA.
That kind of real cooperation is what they're trying to head off, here.