To expand on something #1Flyboy said, your liability insurance, which is valid in the US and Canada is NOT valid in Mexico. You are required by Mexican law to have a liability policy from a Mexican insurance company.
If you have Collision and/or Comprehensive insurance, most likely it won't be valid in Mexico, but it's possible you can get it as optional coverage for an additional fee to your American company.
If you have a loan out on either your truck or your camper or both, the bank probably REQUIRES Collision and Comprehensive insurance,(They may call it 'Full Insurance')so best to sort that out.
Finally, if you have Roadside Assistance, you need to see if it provides coverage in Mexico. If it's one of those multi-tier plans, possibly a higher tier than you now have offers it.
