I liked this one a lot, initially looked impossible, but it sorted itself surprisingly quickly. However, I think you put a comma at the end of your keywords in most of the categories - making a "blank" keyword - which will match any input. So when I put in 'language' for the Estonia group (thinking "countries with a non-indo-european language", which would be wrong, actually), it accepted it.

Nice grid. I tried "Balkans" for the Yugoslav states category, but I think I was on the right track

Correct me if I'm wrong, but can't Azerbaijan and Kazakhstan be switched?

Nice quiz, clever groups. However, some of them have alternative links. For instance, the Georgia-China group are all post-communist and all joined the UN relatively late (China was kept out by Taiwan). The islands group are all members of APEC and probably a few other regional treaty organisations.

the z words group is a bit weak