If you are under-insured for a country, auto insurance can usually be purchased on either side of the border. This can be purchased through your AAA club. Have your passport photos and a completed application. There will be a fee involved. Carry both your IDP and your state driver's license with you at all times.
Some countries have a minimum and maximum driving age.
Check the laws before you drive in any country. Some countries have penalties for people who violate this law. As many countries have different driving rules, obtain a copy of them before you begin driving in that country. If the divers in the country you are visiting drive on the opposite side of the road than in the U.S., practice driving in a less populated area before attempting to drive during the heavy traffic part of the day. Be aware of the countryside you will be driving in.