Erm, I'm having trouble taking a political scientist seriously when they use 21st century Japan as an example of a democratic failure considering... it's still a democracy.

It's got its flaws, certainly, chief among them the dominance of a single party. But that party dominates IMHO mostly because of the the way the Japanese political class operates and how people only seem to know how to get into it by building relationships with established members of the class. The political institutions in Japan - the courts, etc - are hardly as poisoned as the ones in the US.

Basically, if Japanese society is at risk (I'm personally skeptical that it is), then speaking as someone who lives there I'd say it's not due to democratic institutions, which are basically fine, and more due to toxic work, social, and educational habits ingrained into the public at large. If American society is at risk (and I think it could well be), then speaking as someone from there I'd say it's not due to the people, who basically do alright on an individual level, but due to democratic institutions being methodically poisoned by a government that rejects the separation of powers the country was founded on.