Greece does not print its own currency, the US does. Greece uses the Euro, which is printed by the ECB, which is not controlled by the Greek government. The US government can always pay its debts. Doing so may cause inflation, so the real return on that investment may not be great, but the nominal return is essentially risk-free.
Greece's relationship to the Euro is more akin to an individual US state's relationship to the Dollar. No US state has Greek levels of debt. Greece's debt-to-GDP ratio was up to 180%. Most US states run at a ratio closer to 5-15%.
Greece's relationship to the Euro is more akin to an individual US state's relationship to the Dollar. No US state has Greek levels of debt. Greece's debt-to-GDP ratio was up to 180%. Most US states run at a ratio closer to 5-15%.