Non-US sites for car rentals have at times included (third party) liability coverage in the US. A lot of the car rental bookings I used to make via a British Airways-related link/site for US car rentals came with liability coverage included. Not only could the non-US sites' rates be cheaper at times, the included insurance coverages for the rental was a bonus for no additional cost.
Even today, I'm seeing this for an ATL to ATL car rental later this month:
Originally Posted by britishairways.com
Includes:
Unlimited mileage
Customer Fac Fee
Third Party Liability (TPL)
Veh. License Fee
Collision Damage Waiver (CDW)
That's for a two day rental with a total price of 1,580.00 SEK for a 12 passenger van from Avis.