I mean, I think it’s just a completely different development model.
China develops for future demand, while the US develops for past demand.
Invariably, developing for future demand sometimes leads to poor development, but those cases are not the norm. What it does allow is taking advantage of economies of scale to improve net efficiency (again, in the HSR example, China incurred 10x the debt to build 50x the rail of California and 150x the rail of the UK). Even if half of your buildup is useless, it’s still more efficient than the American approach.
I’m sure there’s some optimal point in the middle and I don’t think China’s hit that, but I think you’re conflating different issues to justify the lack of infrastructure investment in the US. The thing is, with the massive rural-urban migration in China, it was always better to have excess capacity than insufficient capacity: the urban population is the key driver to economic growth.
For what it’s worth, you can ask people in SF if they’d prefer to live in brutalist buildings for $500/month or pay the exorbitant rents in the area…