We always had the problem of putting Slovenia in one of the slots. If you ask me it's in Central Europe, but historically we ware always put in the Eastern part (but that probably has more to do with politics than geography).
Unless we speak colloquially, then there's an infinite number of groups to qualify. The OP should use some reference to choose categories ( http://news.ycombinator.com/item?id=2147290 ), his are a bit strange and subjective.
Compare that to the amount of options for the US with its 220 mio population.
I'd propose a schema like this: http://commons.wikimedia.org/wiki/File:Europe_subregion_map_...