the answer is because there aren’t enough Americans that want to ride trains and trains don’t go where Americans need to go.
First part false, second part mostly true because of government.
Amtrak’s route map is basically a star pattern out of Chicago.
To get from point A to point B, you gotta go through Chicago.
To a significant degree that is an artificial problem. Passenger rail service in America was undermined deliberately by a collaboration of government and lobbyists for the tire and auto industries after WW II. In Los Angeles, for example, they literally bought up useful transit track and tore it out, to make way for roads and streets.
The Interstate Highway system was the lethal blow to long distance rail travel, as was airline travel, subsidized by government construction of airports and ATC.
Prior to these developments, intercity rail service was viable and extensive. Along the south shore of Lake Erie, for example, there was rail access from Buffalo to Detroit, with every city in between being served. Those private lines all went under with the completion of I-90 and associated freeways.
The irony is that by now, the interstates have created a new alignment of point destinations. While not of the density of the old central cities, projected rail lines could be drawn to follow the interstate corridors with suspicious fidelity and increasing efficiency.
The real problem is the reliance on the government for top down large scale development rather than facilitating market driven enterprise. The old intercity lines were private and small scale, and they made a profit for a long time. they could do so again, beginning with judiciously chosen stems of routes.
IOW, Amtrak is not the near term answer. The Cleveland-Akron Inter-urban, followed by the Akron-Canton Connector, may well be.