Every Australian capitol except Darwin/Hobart and ACT have commuter train systems, and they have the same land mass as the US with 1/6 of the people.
I hate hearing people use the argument you used, because it's just straight up wrong. If American built rail, you'd be surprised to see how quickly development would flock to build around it. American spread out like it did because the nation moved to Interstates.
How do you explain car craze in china. Its the biggest car market in the world and one thats growing rapidly. So exactly the opposite of what you are suggesting would happen is happening in china.
China comparisons makes no sense. Car ownership is not accessible to most chinese they have no option but to build a rail system. It is not because ppl prefer travelling in trains(vs cars) its because they have no other option. You have cause and effect reversed. If everyone in china can afford a car like USA they would prefer American interstate system. Who would possibly want to live in cramped quarters built around rail system when you can live in suburban mansion with basement home theatre system.
Sorry if I sound selfish but it is really scary to think of 1.5 Billion people doing what the 330 million US Americans do.
At some point, I'd argue there is no such thing as sovereignty. I, a neighbor, have a right to not suffocate to death more than you have a right to burn your house to the ground (or I'll take it by force even if I don't have that right).
https://en.m.wikipedia.org/wiki/List_of_countries_and_depend...
Edit: Wikipedia’s article on China says, “Covering approximately 9,600,000 square kilometers (3,700,000 sq mi), it is the third- or fourth-largest country by total area, depending on the source consulted.“ Now I’m just confused. Area of a country seems like something there would be broad agreement on.