North Korea for sure.
Also all those small countries that no one remembers, like Nepal or Mongolia.
And of course countries where BTC is forbidden, like Ecuador
Mongolia does not have a BTC exchange ? Really ? I heard FriedCat set up a mining firm over there. So, I guess they have some local buyer so that mining firm bills could be paid in local currency.
YOu would be amazed but most of central asia countries do not have dedicated bitcoin exchange market, countries like Azerbaijan and Kazakhstan. Bitcoin is legally banned in Russia so they can't have official bitcoin exchange as well...