Since other commenters focus on the negative effects of the default, let me explain the potential positive effects for the citizens of the country of a default

Since other commenters focus on the negative effects of the default, let me explain the potential positive effects for the citizens of the country of a default combined with an exit of the Euro in the case of Greece. (There are no potential positive effects of a default for the US.) The major problem that is facing Greek citizens these days is that because the Greek government's hands are tied in monetary things, the country cannot achieve its full potential. Since Greece was a net importer for a long time, money has been leaving the main part of the Greek economy [1]. Now Greeks no longer have as much money to afford imports - which would be only fair in some sense - but worse than that, they no longer have money to pay each other. This is what causes the very high unemployment in Greece. Now you would say, if you have person A who would like to sell to person B, and person B who would like to sell to person A, and neither of them have any money, they could still do their transaction, and so not having any money to pay each other is not a problem. That is true in this very simple scenario. The real modern economy is much more complex than that, and situations where two people genuinely just trade with each other almost never occur. So Greece has become stuck, people are unemployed, which means that the country is not reaching its productive potential. By re-introducing its own currency, the Greek government could restart the spending cycle. It is without doubt that a new Greek currency (NGC) would immediately drop in value compared to other currencies. There is nothing that can be done about that, and it is the reason why a reintroduction of NGC needs to go along with a default (or a technical default where the debts are revalued once in NGC, so that the exchange rate no longer matters). It is also true that the short-term pain for Greeks would not go away immediately. Imports would be very expensive in NGC and difficult to afford, but this is not that much different from the current situation where imports are difficult to afford because the money is missing. Most importantly, the Greek government would be able to introduce an economic expansion program to put people to work, so that the real capacity of Greece itself would be used fully to the benefits of Greek citizens. Edit: I should add that this scenario has already played out in the case of developing countries and particularly many times in South America, e.g. in Argentina. [1] Of course, there are also very rich Greeks. However, they save their money and don't invest in Greece at this time (because the economy is bad), so their money does not enter into the picture.