Not defending the OP (or continuing their line of thought), but here's an exclusivity argument for why it's difficult to build public transport infrastructure in the US.
The US is special because its cities were either built to be pedestrian-hostile, or were made so during the Depression years when the transport companies went bust.
Now, in addition to the mindset shift, I think you'd need to rebuild entire cities/metroplexes to make the public transport work.
Case in point: the South Bay Area, where I live now. Sure, you can add trains (at a huge cost). But once you get off the train station, where do you go? The sidewalks are those narrow strips separating the roadway from the parking lots adjacent to stores, they are no joy to walk on, and it will take you forever.
Where in Europe you have:
[store][sidewalk][roadway, 2 lanes][sidewalk][store]
Here, you have:
[business][parking lot][impenetrable hedge][sidewalk][roadway, 3 lanes][uncrossable median][roadway, 3 lanes][sidewalk][impenetrable hedge][parking lot][business]
Then, due to the zoning regulations you don't have stores and cafes right next to place where people live - you have huge blocks with nothing in them but houses, houses, houses.
Ditto for business districts.
It's not enough to have public transport, one needs to rethink entire cities from ground up to make them walkable, bikeable - and accessible by public transport - even if it exists.
Another case in point: Seattle. Lacking a good train system, they made the buses work with dedicated bus lanes, which make the buses fast - faster than traffic.
This works because the city has not been developed in the sad way I described above.
As for the suburban wasteland, which makes up huge chunks of the US population-wise, you can throw all your trains and buses at it, and it will be but a drop in the bucket.
Disclaimer: lived half my life in the US, half my life in urban Ukraine. Big fan of public transport, but drive most of the time - and when I don't, I bike, outrunning public transportation in most cases on distances up to 6 miles or so.
EDIT: see the urban sprawl point below[1]:
[1]https://news.ycombinator.com/item?id=16918434