You can default the external debt. Really, it isn't that bad. Creditors will of course try to scare everyone away, but the truth is, it's just the investors trying to get their money back ASAP.
A default is just "i can't pay now, i'm working things out". Creditors, sooner or later, get paid. The problem is that this credit is usually "big league" 10, 20, 30 or 50 years. Which is typical for a large international bank, or credit organization (IMF, World Bank, etc).
So when you're a small guy who saw a 300% return rate in a small period, of course you will get mad. But it's YOUR fault: if the country is paying out such high interest, there is something very wrong and you should walk away. At that point, it's gambling, not investment.