Pretty sure the OP is referring to the more relevant fact that in the last decade they've built over 100 new stations and continue to do so at a rate of about 12 new stations every year, no slave labor involved.
That's an odd take: where I grew up (Korea), everybody loves subway stations, and "I'll bring in more subway stations!" is a reliable way for politicians to buy more votes. Everywhere, including the most expensive districts.
I'm afraid the American phenomenon of turning their nose up at public transportation projects is just that - a distinctly American phenomenon. They don't know what they are missing.
I'm sure it can be attributed to a lot of factors.
Geographically, the USA has a lot of space, so it's relatively easy to sprawl. Some places have to be more space-efficient.
Ideologically, the USA has always been about individual rights, private property and self-reliance. Car ownership fits that model of thinking better.
Politically, private companies have always had a lot of influence over government. When the car became widespread, it was easy to influence governments to build highways, favour cars in roads, pass parking minimums, etc.
Historically, the USA has a history of segregation. Public transit mixes people from around the city, and I'm sure at a certain point in time there were people in power interested on reducing that as much as possible. I mean, there's that whole event with Rosa Parks as an example [1].
Moreover, a lot of the USA is "new". With a shorter tradition of city-building and more of a blank canvas to start, I'm not surprised what people expect and how they try to build their cities is different.
Real question: Why don't Korean car companies lobby against the metro? Same in Japan. In the US, the car companies were heavily invovled in the demolition of some mass transit (post WW2).
When an entire nation has bought on the idea that X is desirable, lobbyists can only go so far: you might as well ask why American factory owners don't lobby against Thanksgiving breaks.
Another complication is that subway stations reliably increase real estate prices, and in Korea everybody desires higher real estate prices for their town. (Of course we then complain that the prices are too high and vote for the opposition. And then we demand the new government to increase real estate prices just for my town. The cycle continues. Don't ask me why, it's a whole can of worms.) In Korea, a company lobbying against subway would fare about as well as a company lobbying for real estate tax hike, that is, very poorly.
