Bitcoin is only banned in Iceland, Ecuador, Bolivia, Kyrgystan and Vietnam. All of these countries make up just 4.25% of the worlds GDP which is a very small amount. It is also worth mentioning that 4 out of 5 of these countries are very much developing economies and therefore the government and banks within these countries need to restrict the use of bitcoin to ensure that they keep the countries financial system denominated in FIAT currencies afloat. Additionally, Iceland (the country not included) already have a very accountable financial system, recently they imprisoned leading banking figures for their role in the 2008 economic crash. Therefore, bitcoin is not as attractive to them at this moment in time.
That being said, all 5 of these countries would benefit from using the bitcoin network on a peer to peer basis and once the confusion and negativity towards bitcoin in stripped away, and people are able to see the true purpose of this great piece of technology, any country that still bans bitcoin use or simply does not use it will be hindering themselves and their financial industry.