but they trade in currency.
I realize that, but there are no situations where countries bartered for at least 100 years. Venezuela today doesn’t barter even though their currency is worthless, they might barter with 1-2 countries like Russia and China because they want military access. Think of Cuba, they have currency that no one wants and they trade with virtually no one.
Even Germany in the 1920s and 30s traded in currency even when inflation was causing people to carry wheelbarrows of money to buy food.
Bartering works between people not countries.