No, bitcoin can't be a national currency for countries that are about to have their currency wiped out. Zimbabwe switched to the US dollar when its currency failed and was able to borrow US dollars to do it. They are now trying to switch back their own currency because they want control over their own currency.

If Zimbabwe's own currency fails, are you going to lend billions worth of Zimbabwe bitcoins to use as a currency? How exactly would the people of Zimbabwe, who had no money for computers, use bitcoins at all? Where are they going to get the bitcoins to use as currency in the first place? And do you think they would be OK with using a system where an anonymous hacker could steal all the government's money overnight or some hard fork done by China made it all worthless? And that's just the start, the list of reasons it would never be done is almost endless.