HSR is a compelling mobility solution which works all over the world.
California? Maybe not so much unless the government banned air travel and even then, would that fill the trains?
Cross country in a nation the size of USA? No nation roughly our size (China, Russia, Canada, Australia, Brazil) has attempted such a thing.
The difficulty with rail in the US is the lavish subsidies for mass motoring.
Gas Taxes and fees pay for less than 1/2 the costs of highways.
It hard to compete when the other guy gets a 50% subsidy