Great quiz, I just have one suggestion - these aren't "the countries whose citizens have won the most Formula 1 championships since the FIA's inaugural season in 1950", these are ALL the countries whose citizens have won it. So the title and the caveat should be changed.
"World championships", unless specified, encompasses both drivers' and constructors' titles. I would suggest changing the title to "World Drivers' Championships" or include the constructors' titles as well.