You can't. Your car insurer needs to be licensed in your home state.

And especially Massachusetts where car insurance is completely run by the government, and few regular insurance companies operate there. (Every plan by all companies costs exactly the same amount - AAA has a 5% discount for members, so the other companies are allowed to offer a discount too if you ask for it.)

You are correct in the "McCarran Ferguson Act" leaves health, auto, homeowners to the state regulators, but it sure seems to be easier to buy my car insurance from a national company then any attempt at health.

Good to know about Massachusetts, I had never heard of a state pulling that.

This is no longer true as of a year and a half ago.

Another change in Massachusetts is that everybody must submit proof of health insurance with their tax return, or else pay a penalty.

Strange, I get full coverage anywhere I go (including other countries).