Well, you want a consistent schema, so you aren't sometimes using language and sometimes using country, but I think the biggest issue to consider is 'how are you handling variants of language spoken in different countries?' eg spanish - spain and parts of south america french - france and parts of canada.
Answering that should tell you how your scheme should work
(but copying the big boys is indeed a decent fallback. If nothing else, the punters are used to it !)