That is only true if the entire global economy is running 100% on bitcoin. The second you need to trade with another economy (like any nation needs to in order to import/export goods), you are bitten by the same issue.
The US is El Salvador's largest trading partner - so Bitcoin's price relative to the USD does matter.
>That is only true if the entire global economy is running 100% on bitcoin.
100% on bitcoin means no services, no goods, an economy where nothing but bitcoin exists. As soon as I need to drink water the price of water and the income of the operator of the well will go down over time because of the fixed supply and the hoarding of currency.
I think there's probably some middle ground here. Like say the national economy is 100% on Bitcoin and then as long as they have a balanced trade with other countries (i.e. no long term trade deficit/surplus) they can deal with those obligations in fiat currency. But I'm just guessing here.
The US is El Salvador's largest trading partner - so Bitcoin's price relative to the USD does matter.