We are U.S./Americans, living in Guatemala...we want to vacation in the U.S. this time by DRIVING up through Mexico and then to the U.S. We have Guatemalan D.L. and current insurance. Mexico requires us buying Mexico insurance. What does the U.S. require?
US laws vary by state, but in general you will be required to have a minimum of liability insurance. I'm not sure exactly how to get US liability insurance for a foreign vehicle, but I would check with the major insurance carriers (GEICO, Progressive, State Farm, etc)
I know that the US allows Mexican vehicles, but I don't know the procedure. I don't know if they permit Guatemalan vehicles, but I imagine they do. I'm not sure if that is part of your question or not.
And finally, one thing to consider is that the trip between Guatemala and Mexico is VERY LONG, expensive (in large part due to the toll roads in Mexico) and somewhat dangerous. I just took the same trip in reverse, and we had three blown tires due to poor roads, and our brakes siezed up. If your reason for a road trip is to save money, you may well actually save money by flying and renting a car in the USA.
Of course there are many other reasons you may want to drive as well. Sight seeing in Mexico on the way is always fun.