The biggest example is Texas, as they have laws that prohibit direct manufacturer-to-customer car sales. I think that Tesla has had some problems in New York and New Jersey as well.

As for California being the "best place," my guess is that it has nothing to do with being the best - it just happens to be be the spot where Musk said, "Well, we need to sell cars in states that won't allow us to sell things. Let's collect all of the infrastructure to serve these people in a place that's already selling a lot of cars. Let's choose California!"