Yes, but the electricity mix will continue to move towards more renewables. Air travel will continue to use fossil fuels.
The real problem with not doing the trains is the right of ways become difficult.
California wanted to build high-speed rail in the 1970s but the car culture won. They kept expanding the highways.
Now they can’t build directly between SF and LA, for example.
People also overlook that trains can make a few stops along the way.
China transports over a billion passengers a year by rail. Put them in the air
Geography and geology make building HSR between LA and SF difficult. You'd need to bore through a bunch of mountains to get to the Central Valley and then bore through more mountains to get to the SFBA.
Commercial jets starting, idling, and taxiing are incredibly dirty machines - it's nowhere near their optimal operating conditions and it's not like they have catalytic converters cleaning up their exhaust.
Furthermore, even though they're not supposed to jettison fuel before landing anymore, I'd find what were clearly oily droplet stains on my convertible's rag-top disturbingly often. Busy international airports are environmental disasters.
HSR seems like a complete no-brainer for domestic travel from where I'm sitting, if only we could get the lines built in the US.
Furthermore, for a given noise level, any number of surveys have shown that noise from planes is more annoying than from trains or roadways.
Honestly the most annoying part of living next to the train was waiting for the level crossing.