> 1) Comfort is relatively speaking entirely irrelevant to the short air trips within the US.
It's not. There is a reason Amtrak is absolutely destroying air travel in the Northeast corridor, especially among business travelers. I can get work done on a NYC to DC train trip. I can't get any work done on the corresponding airplane trip, between the tight spaces, the cabin pressure changes, etc.
> 2) As a practical matter, you don't need to. It takes you 30 extra minutes to get from the outskirts of cities to the centers, versus an extra 8 hours for train travel to get you to the city center. Perspective.
But not all trips are NYC to LA. The shorter the distance, the more time spent getting from an airport into the city impacts the overall travel time. HSR would get you from downtown NYC to downtown DC in 95 minutes. Getting from downtown to LaGuardia is 30 minutes and from Reagan to downtown is another 15 minutes best case, possibly a lot more with weekday traffic. More importantly to a business traveler, that's 45-60 minutes they're probably not getting any work done, while the train traveler is getting work done the extra 25 minutes the train is actually traveling versus the flight.
HSR is supposed to do Boston to DC in 3 hours, versus 90 minutes for a plane trip. Add in airport time and time spent in the airport, the total travel time is probably a wash, but again much of the travel time for air travel is cabbing and waiting in line at the airport during which you can't get any work done. So the HSR still wins.
DC to Boston is about 450 miles. There are a lot of major North American cities within ~500 miles of each other. E.g. Chicago to Toronto, Minneapolis, St. Louis, Detroit, Pittsburgh, Columbus, Milwaukee, etc. There's tens of millions of people in a ~500 mile radius of Chicago, and HSR would beat air travel for those trips.