This isn't limited to the US. For the trip distances we're talking about here European trains are often just as expensive as flying if not more so.
If you go by air, first you need to leave the city to go to the airport, hand off your luggage to a stranger with the promise it will be reunited with you, go through dense security, wait an hour for your plane to arrive, funnel through a single door, sit in a tiny cramped seat, then wait for the whole plane to exit through a single door, go find your luggage, then find ground transportation to the city center.
Any trip that involves air travel instantly adds 3 hours to the process. More if you are planning to go to the airport during rush hour.
I show up 30 minutes before boarding at my small American airport. Add 20 minutes for travel to the airport and 45 for getting out and you’re sitting comfortably at 90 minutes + flight time door to door to anywhere in the world.
In Europe, I agree, it was closed to 90 minutes pre and post flight plus travel time to and from the airport.
I show up to JFK about 45 minutes before boarding in the early weekday AM, or, if I have the misfortune of having to check a bag, about 75 minutes before. (Same for SFO, PHX and IAD.) American airports are far more efficient, for frequent fliers, than European ones are for Europeans.
For good measure. They get it right. If you're rich in Europe, take the train.
[0] American Airlines at my small airport, for two early-morning flights to different destinations, had all checked baggage going through one agent whose intervention was required for every. single. bag. even if checked in with a kiosk. Of course there was no way we could get the bags on, so we were going to miss the flight. But we went through TSA (both Global Entry/Precheck) with obviously too-big bags and liquids, and they said "no way that's a carry-on", and we said we were going to have the gate agent check it for us, and they said good luck.
We made the flight.