The US is pretty exceptional in its lack of rails. There is also a Seattle-San Diego. Enjoyable as a tourist, but probably not suited for business purposes except in the last portions.
In France some high speed trains go now directly to airports (CDG,LYO). So it is becoming possible to chain a plane and a train in a few scenarios.
It's not really that the US lacks rails, we have the largest rail network in the world. The problem for passenger rail here is population density. France is three and a half times denser, and Japan is nearly 10x. I think they would also struggle a bit more to justify rail costs if they were as spread out as the US.
For freight[1]. Putative high speed rail might go to the same places but generally can't share the same tracks with 30mph long haul trains. And the big gap is the plumbing of rail and transit into the urban cores, which in most US cities is highly decayed and in many of the newer metropolises was never built at all.
[1] Which is unsurprising, because we have the biggest per-capita need for transcontinental land freight transport in the world. The US has been perfectly fine at building out infrastructure it thinks it needs, it's just been making poor choices about what it "needs".
Looking at gross population density misses the mark completely. The US has a large land area where approximately no one lives: most of Alaska, the Great Basin region, even the High Plains are thoroughly devoid of population yet take up millions of acres of land. Cut out that area and focus on places where people live, and the density is now much more comparable. The Midwest is about the same density as France.
The evisceration of the passenger rail market was in large part caused by intentional urban planning. White flight moved a lot of people from city centers to suburbans where nary a black person could be found, and urban planners in turn abetted the process by building freeways straight through urban cores and turning every other city block into a parking lot in all but the very largest cities (well, except for LA). Uncoincidentally, the cities that didn't get turned into massive parking lots retained much more functional commuter rail systems than those cities that did.
Indeed. Even most of the states with low density tends to have most of their population in much smaller urban areas with density comparable to European countries with decent systems.
E.g. Utah has a population density of 14km^2, similar to Norway. But like Norway, Utah has most of its population in a small portion of the area - the Salt Lake City–Provo–Orem Combined Statistical Area makes up 82% of the population.
Nebraska has a density of 9.63km^2, but Omaha-Council Bluffs + Lincoln makes up more than half the population (and that's ignoring the Iowa side of Omaha-Council Bluffs)
There are plenty of metropolitan areas like this in the US that may not have the density to justify much of an expansion to rail between them, but that are dense enough that a more rail oriented infrastructure within them would be possible.
And as you point out, this is with current US urban planning. If an expansion of rail is combined with adjustments to urban planning to encourage construction aligned with expanding transport systems, it'd become even more viable (e.g. near automatic planning permission for higher density near stations would probably in itself do a lot)
I don't think the population density alone explains it. The part of the Finland that is covered by rails is a bit less dense than US, but the overall inter-city train usage is about 3x more than national air travel (2019).
There a lot of second tier cities in the US with sufficient population but still have shitty rail service because freight gets priority, slowdowns from track maintenance is constant, and the stations are in unsafe locations.
Population in the US is not uniform. Out east we are as dense as Europe. Even the Midwest isn't much less dense than France for selected areas the size of France. Then there is the vast amount of nothing out west.
> In France some high speed trains go now directly to airports (CDG,LYO).
... The trains departing from there are mostly low-cost trains rather than trains meant to be connecting with flights, and people taking them have to move to CDG instead of a better location.
It seems to be a service aimed at salvaging the infrastructure rather than an actual useful service.
One of the best examples of air/train integration is Frankfurt, which has the high-speed trainstop underneath the airport. You are much faster on the train than getting into your car and you pretty much have an ICE going to Cologne, Hamburg or Munich (not sure about direct ones to Berlin), going every 45min or so.
In France some high speed trains go now directly to airports (CDG,LYO). So it is becoming possible to chain a plane and a train in a few scenarios.