1. Many Russians held funds in currencies other than rubles. Faced with sanctions, Putin instituted forced conversion to rubles. So far the ruble hasn't been decimated but this could still go south;
2. Venezuela essentially prevents conversion of currencies. I mean it's complicated. There's a government rate and a black market rate and the country is under completely unjustifiable sanctions; and
3. Argentina is also currently restricting access to foreign currencies;
4. Years ago, Argentinians held funds in foreign currencies. Local banks held foreign currencies against those deposits. When things went south the banks basically packed up all their money, put it on a plane, flew it out and then declared bankruptcy or just threw up their hands; and
5. Some will even point to FDR's sovereign devaluation of the US dollar as another bad example. In the 1930s, the government forced purchase gold for $20/oz (the peg at the time) and then revalued the US dollar at $35/oz.
This last one is a constant point of consternation for gold bugs turned Crypto Andys.
And no crypto isn't the answer here.
My point here is that you cannot overstate the importance of multigenerational wealth creation in the developed world. The dark truth here is that the US has often had a hand in the above events that have essentiaally stolen accumulated wealth from ordinary citizens.