Compare this to Japan, where transit is still going strong because the highways must recoup revenues via tolls.
One huge difference between the US and Japan here is parking. Having a car is one thing, but where are you going to park it when you arrive at your destination? If you're driving between two towns or smaller cities, this might not be an issue, but if you're driving between Yokohama and Tokyo, it probably is. The car is only a feasible choice if you're traveling between points where there's a place for you to park. So of course, this drives a lot of traffic onto the trains and keeps ridership very high.
This is entirely a policy choice. America subsidizes parking by requiring very high parking per place, and since they’re required to build it anyways and there is so much supply it is always free.
Japan does not subsidize parking like this, in fact quite the opposite. There is no free street parking and to buy a car you need proof of a parking spot to store it in, and parking is more of a market as a result.
Transit systems need to be about twice as fast, comfortable and convenient as car options to be competitive, and in the US political and operating environment of the last 100 years, it's not happening. Suburbs broke two major rent-seeking dominances-- urban property owners AND transit unions. Together those actors preserve a terrible experience and the path to a car-free future is doubtful precisely because it would require overcoming those social groups in addition to solving major technical and capital problems.