General Discussion

- The rental car companies have always warned me against even thinking about taking it across the border. If you ask, they will tell you to drop it back off at the lot, or park in the Border parking lots, take the Blue line to the border, walk across, and rent another car in the many rental lots in Mexico set up right along the border - just for tourists who want to go to Ensenada, travel on 2D on a brewery, hot springs, and spectacular high desert day trip from TJ to Mexicali, or head down to the Gulf of California for some fishing.

It's not just in the small print like with most car rental documents, California rental companies tell you up front before they give you keys.
When I rented a car in VA or FL on work, it was a little paragraph on the rental form. Easy to miss or ignore if you're picking the car up at an airport in, say, Denver.

Likewise, when I was growing up in Seattle, our HS soccer team had to get special consular permission and everyone had to sign international travel paperwork to take a school bus up to Vancouver BC on a exhibition game - and that was in the early 1970's.
And in those days, we could just cross the border in the family car with dad's driver's licence, proof of registration and Canadian insurance (purchased for the trip in Seattle or Blaine, if dad forgot) if we wanted to go up there.

It's not Canada being pissy about expired visas. It's the rules bringing a rental car that doesn't have the insurance or other paperwork to drive in Canada.