Viable passenger rail service depends on sufficient population density. Other than within metro areas, the Northeast corridor is pretty much the only place we have population density comparable to Europe. I like traveling by rail when there's enough demand for it to have a regular schedule with lots of trains at convenient times (for instance in the UK or between Philly and NYC or as a way of commuting, as I did both my last two years of grad school at Penn and when I went back to visit Penn on sabbatical). I live in Kansas now. There is way rail service will compete with the automobile (and air travel for getting to far away places) out here in the Great Palins.
That is and ain't true... Many on the Empire Builder's route (Seattle to Chicago) are very reliant on the rail... Not very long ago it was not uncommon to go on up to Whitefish (15 miles north of here) to pick up people and freight... No more...
But that is largely to do with how the feds tried to make rail travel profitable - in their wisdom, they just jacked the rates till no one can afford to go by rail...
Quite the other thing should have happened. Rail is uniquely the only form of travel that can handle influx... Too full? Stop along the way and bolt on another car... And the same the other way around...
I think LOWER prices would make it more attractive. And standard, reliable pricing at that.
On average, I think it is about 400 bucks round trip for a ticket from Whitefish Mt to Chicago Ill...
For that, in about a day and a half, you can travel the roughly 1800 miles in reasonable comfort, with good access to food and drink and zero effort...
WAY better than by car. And you arrive refreshed, and probably quicker by some hours - I have made that ride in 22 hrs by car, but that is really flying low, and it takes half the time I am there just to recover from the trip! Just to do it again on the way back...

But to my point: If the rail were cheaper, it would leave some room for folks to rent a car at their destination... For instance, not many folks will use the train to get to Missoula, which is 120 mi south of here, because once they get to Whitefish they have to rent a car to drive the 120 miles to get on down to Missoula, and the same going back. For that extra cost, they might as well use air and get there way quicker direct, at a pretty comparable price (assuming of course, advanced booking).
In that way, I think they have priced rail away from markets they could otherwise pick up... And thereby make the difference in volume... Not to mention butts in the seats meaning more concession, which also cannot be ignored...
And berths should be standard - No one wants to sit in a dang airline-style seat for a day and a half... At least a bunk available to sleep in would make it more attractive.