Most likely, all countries will really switch to cryptocurrencies, but not the cryptocurrencies we all want, because many countries are working on creating their own cryptocurrencies. I doubt that, for example, all countries will legalize Bitcoin in the near future, but I believe that this will happen in the longer term. Perhaps in addition to BTC, other cryptocurrencies will be legalized, for example, such as ETH, XRP, XLM, TRX and others.
Cryptocurrency has an indefinite status in many countries, but in most it is legal, even if it does not have a legal status.
If everyone switches to cryptocurrency, then the already extremely manipulative world political field will turn into a battlefield, where the main weapon is the manipulation of cryptocurrency rates.
Rather, then everyone will create their own stable coins, which will not differ from ordinary national currencies.
More precisely, crypto does not belong to the government, it is not in the illegal and legal, this choice is up to the government but it has no actual value, and if countries turn to crypto, more economic battles will occur as you say because this system does not have a price regulation, the price is based on the desires of a group of people, and when countries join and allow people to use it, the manipulation will be at a terrible rate every day. Therefore, most countries are restraining each other, not allowing to establish a secure bridge to crypto, too many threats.