It really depends on the part of the US. Amtrak is very reliable in the north east. Lot of the commuter train services are quite good as well. Subways and metros are pretty good in most of the north east as well.

Amtrak is much more limited in its coverage on the west coast, but still ok from what I’ve heard. BART in the SF area has good ridership although it needs some more investment, LA is doing some big expansions right now as well.

Chicago has a good but a bit old transit system as well. The Amtrak from NYC/DC to Chicago is a long but pleasant ride, about 18 hours; but this is to be expected given that the distance is 1146 Km (714 miles) which is about the same as Brussels to Warsaw, and most of the routes for that appear to be about 18 hours as well.

I’ve heard some rumblings about projects in the Pacific Northwest, but it’s not really something to write home about as it stands. Needs more investment and not to have the projects price gouged by contractors.

Some mid sized cities and towns all over the country will have decent bus services, some even a light rail or two, but it’s a coin toss.

The South West, Mountain west, South East and Midwest (outside of Chicago and the twin citiest) absolutely atrocious, like, you are basically screwed if you don’t own a car. Like there are a few example of decent local transit systems in particularly big cities but their ridership and coverage are pathetic given the size of the cities and there aren’t any plans for serious expansions on the scale that needs to be happening. Regional rail is just… hope you like a 2 week train ride where you’re spending half the time waiting for 40 mile long trains full of gravel to pass.