I was almost going to disagree with you, but your last paragraph includes the part that I agree with! 🙂
With developing public transportation, legacy infra has nothing to do with the difference between China and the US. Most of China's rail infra was built in the past 20 years. They've *added* more miles of commuter rail, than the US *has total*.
In terms of underutilization, one way to look at that, is that they've invested in the infra, and hope to grow into their shoes.