Biggest obstacles to high-speed rail in CA are right-of-way acquisition costs, terrain, and NIMBY-ism.
Right-of-way: Virtually all of the projected route is privately owned, and it ain’t cheap. We don’t have the option of forcing out the current owners / residents with rubber hoses and tear gas.
Terrain: We have non-trivial mountain ranges to deal with … in earthquake country no less. In contrast the Beijing-Shanghai route is flat as a pancake. Maybe they could extend it as far as Wuhan without problems, but the costs would skyrocket if they tried to build out to Fujian or Guangdong.
NIMBY-ism: Palo Alto, Menlo Park, Atherton, and San Jose are already banding together in opposition to high-speed rail. Is this because of “environmental impacts,” or because high-speed rail will diminish the location premium factored into local property values?
It’s not because we (technically) can’t … it’s a matter of feasibility.