There is no such thing as a citizen of California. Every citizen of the US (except the ones out on bail, incarcerated or on probation) has the right to move to California at any time, which is the big flaw in your idea: if California were to start to subsidize healthcare for every California resident, hundreds of thousands of sick US citizens who currently cannot pay their medical bills would move to California, putting a politically unsustainable burden on California's taxpayers.

Subsidizing health care in the US has to be done at the Federal level. The Federal level can require the states to contribute, and I think that is what the Federal Affordable Care Act does, but that is politically palatable only because all 50 states must contribute.

Well, I'm sure Californians, who value democratic principles highly, will gladly accept migrants, who in turn will help to build the state even stronger.

Also you have somehow assumed that a person with health problems is a net burden for the state. When all the progressive humankind have recognized that disabled people can and do contribute a lot to the society, you are dismissing their contribution calling them "a burden".