I'm 99% sure there's no nationality factor.However, there was a slight modifier for very young players, although I don't know what that modifier is.
Maybe I am wrong -- at one point I thought the goal was to preserve the best players, per nation, so that the FA number was adjusted depending on the maturity of the league. So I "catalogued" this concept in my head and haven't thought about it much since.However, given that I haven't seen too many free agents recently it is likely that I am incorrect and you are right.