I disagree with all three assertions above - the dififculty increases exponentially for the last few percentage points, just like energy required increases towards infinity as you approach the speed of light,

California is a small part of one country.

All we will get out of self-driving cars is more traffic jams, more consumerism, and less security in our lives because you might be locked out of essential service in case you didn't sign a lisence agreement or made an offensive tweet, or replied to a spammer

California weather is very forgiving even if you account for places like Tahoe. AFAIK, none of the self driving companies have much experience with scenarios like New York in winter.