So are Prudential, New York Life, State Farm, Progressive, Aetna, etc.
They are still regulated at the state level, so every insurance policy they sell must meet the regulatory requirements of the individual state where it is sold. I believe most of these companies maintain separate subsidiaries in each state where they operate.
We are in the process of a new start up biz. We have to be registered in every state. Every state has different rules and regs and reporting requirements. Some states require a surety bond.
Why should any other biz be any different?
As much as I hate Obamacare, I have to admit half of the problems with it already existed at the state level in many states. For instance, when I was young we could buy catastrophic-only insurance which had low premiums because it didn't cover normal doctor visits. So anybody could afford insurance. But state regulations in Alabama and almost every other state made those go away, you know to help us have only "good" insurance policies to choose from (read: expensive only). Then Obamacare came and made it a national problem too. (Among with the many other things Obamacare brought.)
The only thing good about Obamacare IMHO was dropping the in-state-only regulations most states had. Of course, it didn't matter to prices because the same Obamacare mandated all insurance polices be sorry in quality and expensive in price (to cover pre-existing conditions).