The Japan government has a huge debt. But it is mostly owned by Japanese people and firms. If you look at the whole Japan country, state, people and companies together Japan is not in debt, but is a net creditor. So very different from the US as a whole.

The Social Security Trust Fund used to soak up most of the U.S. deficit, but it switched to net outflows 1 or 2 years ago.

For the past 5 months the Federal Reserve has increased its treasury holdings by $250 billion[1], after selling them steadily for the past 2 years as part of QE reversal. Everything I've read said that the recent inability for the Treasury to clear short-term bonds is a technical issue. But I wonder if these two matters are purely coincidental. Perhaps the removal of the SS Trust Fund buffer is starting to catch up with our massive and dramatically increasing (since the Trump tax cut) deficits? Any linkage would have to be indirect, I suppose, but still....

[1] https://fred.stlouisfed.org/series/TREAST

I wouldn't say that. They have been suffering from a lost decade that has lasted 30 years. Social stagnation is the highest it's ever been. Yes, there is still a lot of social cohesion but that's maybe just... because they're japanese? Japan is the country where fining families for an suicide that stops the train works because suicidal individuals don't want to inconvenience their families.

Japan is also a country with excellent infrastructure, low crime, clean streets, and great universities.

“Lost decade” relative to previous growth. Relative yo the rest of the world they were and still are far ahead.