New York to San Francisco is roughly 3000 miles (4800 km). At 250km/h, that’s a 19 hour trip.
A 19 hour plane trip from New York gets you to Singapore.
Fast trains are great for journeys up to about 600km. For crossing continents, planes win, whether rail enthusiasts like it or not, and a future of transport that involves “just don’t fly” as the only solution to climate change is an absolute nonstarter in most of the world.