What if the government of a country is irresponsible and issues a large amount of currency to buy Bitcoin?
No matter what the reason is, inflation is already very serious now. If some unscrupulous governments print a lot of money in order to repay debts and fight inflation, of course it will not be one time. Credit money no longer has credit.
When a chain of interests is formed between big countries, behind the crazy printing of money is the harvesting of countries that are not rich. What would it look like if it were all exchanged for Bitcoin?
AFAIK, if a country is planning to print as much money as they can, there's a governing international body that has to be informed doing that so they'll be monitored. There are some legitimate reasons why it can be done but I don't think that they'll ever allocate to do it for bitcoin.
Unless that country is really a bitcoin nation like El Salvador but even them, they are not telling that they've got plans like this because I think it may not be impossible but highly unlikely.