> How can they be having a currency crisis when they don't have a currency?

You're right. It's technically a balance of payments crisis.

At the brink, and from outside, they model similarly. Deposits in El Salvador banks start behaving like a currency as international depositors haircut against the risk of seizure and capital controls. From inside, they're different as the long inflationary phase of a currency crisis is truncated to a default and reset.

This makes it sound as if El Salvador should have introduced something similar to the Chiemgauer in Germany. Basically it is a local currency that keeps money within the region, it has a circulation safeguard which is supposed to prevent stagnation which is how most complementary currencies die. The interesting part however is that it is 100% backed by euros. The circulation safeguard and the trade in fee make the Chiemgauer just a tiny bit less valuable than actual euros. If El Salvador implemented such a system it would be dollarized but at the same time have a slightly devalued exchange rate vs the dollar which discourages imports and encourages exports to the US.

What El Salvador is experiencing is basically the North American equivalent of the Greek economic crisis.