This link argues this sort of thing is not a question of appositives:
*"This is not apposition, as there is not a direct re-addressing of the referent. Contrast: The bathroom, the smallest room in the house, is on the first floor. = The bathroom, [which is] the smallest room in the house, is on the first floor. // Sally, [who is] their eldest daughter, is getting married next week. /// Sacramento, which is CA, … Here, you need to insert the preposition ‘in’, showing the non-equivalence of ‘Sacramento’ and ‘CA’. /// As stated above, readability rather than rules-of-thumb should be the guiding factor here (though it would admittedly be best not to annoy the PO)."
I can tell you that both English-language dailies in Thailand omit the second comma in such geographic instances.