The US dollar has been the global reserve currency for the last 60 years or so. However, Russia and China are both indicating that they want to move off the US dollar system, having voiced concerns over how expensive it is, and the fact that the US weaponizes their currency on a shockingly frequent basis (see Iraq, Eritrea, Haiti, Laos, Lebanon and around 25 other countries with US imposed sanctions and embargoes).
China and Russia are always welcome to start using whatever currency they want, but their broke-ass economy wouldn't be able to handle the consequences of it.
Whether youre an individual or an entire country, the option to resist seizure and censorship is probably of much more importance than volatility, liquidity, or adoption. Bitcoin cant be taken away from you, unlike the US dollar.
Wrong. The risk of seizure of countries assets is extremely low, Russia, China, Iran and other countries keep violating human rights and international laws, and they get a slap on the wrist at worst (sanctions against individuals). But losing 80% of your reserves value in a matter of a year can easily wreck your economy for years and even decades.