Passenger lines in the US have been slowly shutting down for decades due to lack of ridership. The rails are still there, hence the cargo routes still being active, but passenger trains have been going empty on all but the most popular routes.

The biggest part of the issue is that the US has the best highway network in the world, fast and efficient at getting anywhere. My girlfriend and I used to travel from Wash DC area to Miami area every year to visit family. We have 3 options to get there:

1) When we were broke in our 20s, we would drive and it would be a single day of driving for 14 hours from 6 AM to 10 PM and about $100 worth of gas. Both ways, we'd spend 2 days of our vacation traveling and $200 on gas. Plus we'd have our car to get around while we're down there.

2) By train it would by 28 hours and $450 for 2 tickets. Round trip that's 3 days of our trip is spent traveling and $900 for tickets. Plus we'd have to rent a car for the week at about $350 dollars. So you're looking at 3 days of your week vacation gone and $1200+ for travel.

3) By air its a 3 hour trip and $300 for 2 tickets. Round trip that's half a day of travel and $600 for tickets. Plus the rental car for an extra two days is like $425.

So when we were broke in our 20s, we drove because it was cheapest. As soon as we could afford to spend a bit more on vacation, we just jumped straight to flying, because its both cheaper than train and at 8 times faster we got 2 extra days to spend in Miami.