I would have to agree that geographic names in and of themselves don't necessarily mean anything. The only examples so far that would seem to really imply anything is the Union Flag and the description of Riker being 'countryman' to historical Americans, and the flag could easily be nothing but local nostalgia.
I think it may also be wise to consider that - even if there are governments in the 24th century which share the same names as modern govts., that doesn't necessarily make them 'the same governments'. In fact, the history of Trek's WWIII would seem to suggest that most old governments were completely destroyed.
Maybe when the united earth government was formed after First Contact, it was just deemed most convenient (or least objectionable) for the regional and local subdivisions of the new government to be based on and named after the old independant nations.