If your investments are all inside the country That defaults on its debt then yeah your fucked anyway, but if you're investing in a country's debt and you have little other exposure to said country, then their defaulting on the debt is the only thing that's fucking you. Argentinas default is the best example of this problem.
Unless the government, which has the power to break the agreement, breaks the agreement.
The history of finance is well-woven with the thread of sovereign defaults.