If Bitcoin becomes the major currency of every country, in countries where the inflation rate is at double-digit, it won't be that bad again. The major cause of inflation is devaluation of the currency, so it is no longer able to afford what it could previously afford. This leads to an increase in the prices of goods and services in the country. But with the scarcity of bitcoin, that won't be a problem.
Also, the political and economic unrest of the country won't affect their currency. I think it will benefit 3rd world countries the most because they are the ones with failing currencies, economies and political systems. All these are just hypothetical, though, because I can't imagine a world where Bitcoin becomes the main currency.