insurance not paying

got hit by a proffesional mexican driver with american insurance for foreign companies. his insurance does not want to pay because the mexican registration was expired at the time of the accident, though the california registration is still valid and on his insurance policy that is the only registration mentioned.
My insurance would not pay because I had only liability coverage, and closed the claim.
What should I do?

just because the insurance company does not accept the claim does not mean you can not sue the driver and the company he works for
see if they have a local address on this side of the border
then file a complaint with the department of insurance tell them there is a company operating trucks without valid insurance then go to your local congressman see what happens
you can get the number for the department of insurance in the white pages under state government