There was an African country which has failed currency that essentially by default switched to Bitcoin (sorry I cannot remember which one).  But in general more wealthy countries will use Bitcoin since they are more likely to have access to the internet and computing devices that can support it.  Also keep in a mind a lot of exchanges don't allow certain countries to buy as well.  This is why I think a coin like Lumens and similar is a smart bet against Bitcoin as it really is too expensive and slow to use for daily transactions or to "truly be your own bank".