Sure, but… cities in the USA are thousands of km. Seattle to Chicago (the example given by the GP) are 2800 km distant. Those cities are slightly more distant than Lisbon and Warsaw. Chicago to Washington DC is almost the exact distance as London to Marseille (1000 km). Chicago to Houston, Texas is the same distance as London to Rome.
To go back to the first example, Seattle to Chicago is a 4 hour (scheduled, which already includes taxi time at both ends and a buffer for late departures) plane ride. Even a TGV running continuously at top speed (320km/h), with no stops, would take 8.5 hours to complete the same journey. Wikipedia tells me that the fastest start-to-end scheduled speed of a TGV is only 280 km/h, which would take over 10 hours.
Chicago to DC is about the break-even distance for high-speed-rail vs. flying. That's already pretty darn good, and it would eliminate a lot of flying.
To go back to the first example, Seattle to Chicago is a 4 hour (scheduled, which already includes taxi time at both ends and a buffer for late departures) plane ride. Even a TGV running continuously at top speed (320km/h), with no stops, would take 8.5 hours to complete the same journey. Wikipedia tells me that the fastest start-to-end scheduled speed of a TGV is only 280 km/h, which would take over 10 hours.