Cool game. I also had a string of very easy questions early on that almost made me leave the page, so I think calibrating the difficulty is important. Maybe even start presenting harder or easier questions based on how the user has been performing.
Thanks for the feedback. I have to plans to make the match ups closer (explained in my other comment to rollo_tommasi), but I like the idea of scaling the difficulty based on the score.
One suggestion: Adjust the game so that the player is only presented with countries that have populations within a certain distance of each other. Right now I'm getting a lot of "Marshall Islands vs Pakistan" type questions.
I plan to implement this soon. Right now each country is chosen randomly. What I have in mind is to sort the countries by population and choose the first one randomly. Then, choose a second country that is random, but within a certain distance from the first one. i.e. within 10 or 20 spots on the list. Hopefully this will ensure closer match ups.