US Car insurance, now living in Germany

Hello everyone!  My wife and I moved from Houston, TX USA to Mannheim, Germany earlier this year - it's been great so far!  I am on a 4 year assignment for work, then we will move back (somewhere) in the US.  So, we still own our home in Houston, TX, but we sold our cars.  It's pretty liberating and awesome to not have a car and still be able to get around.

Question 1: Auto Insurance
As mentioned, we sold our cars before moving to Germany, and haven't (and don't plan to) purchased cars here.  However, I maintained my US auto insurance through Progressive, since I may drive rental cars or my parents' car when visiting the US during holidays.  I really want to cancel the insurance, but I kept it to ensure I have liability coverage (accident coverage can be achieved with credit cards I have, or at worst case, including it in a car rental agreement).  Is there a way I can cancel my expensive Progressive insurance but still somehow be covered with some sort of liability insurance in case I drive a car in the US or abroad?

Question 2: Home Insurance
As mentioned, we still have our home in Houston, TX.  We have tenants renting the home.  The tenants have home/renter insurance on the home.  However, I maintained my same exact home insurance converage on the home.  Is there a better / cheaper insurance coverage for a home you have tenants living in who have their own coverage?  I know it is wise to still protect myself with insurance on the home, but are there better strategies for this to save money?

Thanks for the help!!!