This country is so large (and that's only the 48 continental states) that it's never a good idea to compare trains, or possible train routes, here to those in western Europe, or Japan, unless you are only speaking about the northeast corridor. That part of the country has decent train service.
In 2001 I was on a driving trip through Colorado and South Dakota, and somewhere in SD stopped in a small town that had turned its train station into a local museum. The date of the last passenger train to stop there was noted prominently. It struck me as both sad and criminal that they'd been without train service for some 20 plus years at that point. Not to mention, that if you're talking about small towns and rural areas of those places: South Dakota, North Dakota, Montana, Wyoming, Minnesota, and various other large states out west, you can easily live several hours from the nearest airport. That actually has commercial airline service.
Until deregulation took hold, the airlines did a good job of serving small cities across the country. There was an entire system of local airlines -- you may remember some of the names: Mohawk, Piedmont, North Central, Bonanza, and others -- that flew smaller, older aircraft into such smaller cities as (just to name one state that I happen to be familiar with): Watertown, Ogdensburg, Massena, Elmira, Ithaca, Jamestown, Olean, Binghamton, Saranac Lake, Utica, Glens Falls, Plattsburgh, all in New York State. I don't believe any of those cities have air service any more.
I currently live in Santa Fe, NM. When I first moved here in 2008 the local airport had no commercial flights. A few years ago American and Delta resumed service, flying regional jets from here to Dallas and Denver. For a while American had a flight to Los Angeles, which they unaccountably discontinued. Unaccountably as there is a lot of film and television production in this part of the state, and the only times I took that flight it was completely full. Nowadays there is one flight a day to Phoenix, as well as DFW and DIA.
That's just one small example of a small city (and the state capital) that is grievously underserved.
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