I'm not going to pretend that I know the whole picture as to why this project is so severely over budget and behind schedule (there is likely nobody on Earth who does), but let me give some pointers as to why countries like China have built hundreds of thousands of kilometres of high-speed rail while California struggles to build a few hundred.

For one, the legal environment in China is one of the prerogative state. "Rights" in China are whatever the Government suffers you to have or deems it expedient to honour. So if you "own" a piece of land in the middle of the planned rail route, the Government will just kick you out. What are you going to do, sue? In the US, environmental laws, land rights laws, and legal procedural law mean that anyone who can spend $50,000 on a lawyer can cause $1 million worth of headaches for the high speed rail authority using the American legal system, which believe it or not, actually sometimes holds the State accountable to the law.

Secondly, in China, the Government has an unprecedented control over the economy that allows it to offer carrots and sticks to a degree that American politicians could only dream of. Yes, you have no say on whether the Government will order your house demolished to make way for an expressway, but in return, if you go quietly, you'll get a flat in a high-rise in exchange and generous monetary compensation. Raise a stink, and you'll be paid three strawberries and a steamed bun for your house instead.

Thirdly, under Chinese property law, all land in the country belongs to the State. Everyone else can only lease it from the State.