OK, so I just did three tests in a row... And, tonight, here are my results:
USA Challenge: got to level 8 with a score of 15,813 (18,000 points needed to pass level
World: got to level 8 of 12 with a score of 25,766
And now... for the miserable Flags test: got to level 2 with a score of 9953.
So, it's even harder than I expected because not only do you need to identify the flag, but you also need to figure out factoids about the country (like capitol city, etc.).