Developing countries have the opportunity to spread for bitcoin. But it can be a revolution for countries with a poor economy. People can keep the money as bitcoins so they don't lose value. In this case, the official currency collapses. Bitcoin price movements can make the economy much worse.
If at any point in time bitcoin really becomes widely adopted by the population of a country and they prefer to use it over their currency then bitcoin is not going to be the reason for the collapse of that currency.
Bitcoin will be nothing but the symptom of something going horribly wrong in the economy of that country, but while bitcoin has been adopted in some countries with economic difficulties that adoption has not been so widespread so we have no idea if this is actually going to happen at some point in time.