As the "densely populated area" remark should give it away, I do not claim that USA should build metro lines between cities. What I say that cars in cities are not the solution.
Funny enough, I am in Istanbul since a while. I flew from London to Istanbul, it took me about 8,5 hours I guess. 30 minutes to Heathrow, 2 hours at Heathrow, 5 hours in the plane(did not take off immediately) ,1 hour at Istanbul Airport, 1 hour on a bus to my destination. Definitely better than the train but only because there's no direct line. The trains in Europe are great but expensive. If there was an overnight train to Istanbul from King's Cross at reasonable price I would have taken it.
The mass transit in Istanbul is horrendous but wherever available, the metro is much much better than the Istanbul traffic. Admittedly, the car could be better if you are in an S class Mercedes and being chauffeured.
The snark is unwarranted, it is unwelcome, and it is against the guidelines for this site.
America is absolutely enormous, sprawling, and suffers from a relatively recent inability to build things, which is very frustrating indeed.
If we were to cram our entire population into, say, Michigan†, I doubt we would have given over our extensive rail network to freight. But, we did, and Los Angeles tram system was bought out in a shady backroom deal, and there were other various and sundry sins. But mostly, we invented jet travel, and trains just don't cover the 4500 kilometers between New York and Los Angeles in an appropriate amount of time.
Admit it: if you were going from London to Istanbul, you could take a train, but you would fly. Well, London to Istanbul and back, that's the distance from New York to Los Angeles. Which you can do by train! But, people don't.
California, that notorious bastion of communism, voted in a high speed train between San Francisco and Los Angeles, and is still waiting for what they paid for. LA has added quite a lot of Metro in the last 30 years, but with a mere 150km of rail, 93 stations, and only a hundred million yearly riders, there's a long way to go. Meanwhile SF can't get the BART to circle around the South Bay for love or money.
† The size of the entire UK, and there are ten states larger.