It's a nice thought, but economically speaking, even if massively adopted, BTC couldn't save a country from bankruptcy. A currency that they cannot control wouldn't become the primary currency of a failing economy
A currency that's actually useable & trusted by the people is better than the debasement of banks & greed of government officials.
How would that be different in BTC, where you have greed of early adopters controlling tens of thousands of BTC and effectively being able to manipulate currency acting as central banks?
A better way would be some sort of PoS crypto split equally between all countries according to their population numbers, or even better, split equally between all individuals.
But both plans are utopia anyway, not worth writing a few words about.