Because the US is overwhelmingly urban sprawl and is not Europe. The only way to fix this is to tear down and rebuild (which we cannot afford), or accept that public transit wait times are terribly slow due to the distance between stops.
Combine that with a lack of nerve to aggressively combat crime or antisocial behavior on transit, maybe a fear of perpetuating inequality or something, and anyone who isn’t a man doesn’t feel safe trying it.
That's a bad excuse
a) because Europe isn't one single demographic but still public transport is useful, reliable and safe everywhere (from Dublin/Zurich on the low side of the population density scale to London/Paris/Madrid on the high side and Amsterdam/Hamburg/Prague in the middle).
and b) there are plenty of examples outside of Europe. Melbourne is urban sprawl. The metro area is 50 miles east to west, 30 miles north to south (more, but there's also a big bay) and a population of only 5 million. A lower population density than the Denver MSA but manages to run a train/bus/tram system that's useful, reliable and safe.
Blaming sprawl or population count, while being outshone by Canada, means it's neither of the above. Perhaps we can move on to the auto companies pushing out light rail in California in the fifties to bump their own profits, or accept that it's the American people and their ethos that has left the automobile as the claimed only option.