Cool idea! Just wondering--does the source not include some countries? For example, I would think that Vatican City should be at the top of the list with 100%.
Maybe you should say something about that? As the red letters indicating small states seems to indicate that it does include such tiny countries. Not that this is hard to figure out given the hints.
Great idea but giving us the city turns the quiz into a game of 'name the countries these cities are in', which makes it quite easy. Only having the percentages would make it a force to be reckoned with.