Nonsense. The US has the largest freight rail system in the world, and is considered to have the most efficient rail system in the world to go along with it.
There isn't much in the way of passenger service, granted, but that's because people in the US aren't, well, poor. They can afford better transportation options.
> It turns out that boom-and-bust capitalism isn’t great for building something that needs to evolve over centuries.
It initially built out the passenger rail just fine, but then evolution saw better options come along. Passenger rail disappeared because it no longer served a purpose. It is not like, say, Japan where the median household income is approaching half that of Mississippi and they hold on to rail because that's what is affordable.