Countries with a weak currency can greatly benefit from this. In fact, the presence and importance of Bitcoin is something that can be noticed strongly in such countries, as Venezuela.
No one wants to depend on a currency with astronomical inflation rates, and Bitcoin is one of the few affordable alternatives for a large portion of the population of such countries.
I think that the Countries that have a weak Currency can just invest into Bitcoin then make a bunch of money into it and it would eventually help their economy. The people in the Country that invested in Bitcoin wont need to invest all their money into it and the price of Bitcoin would give them enough money to strive on.