America's "secret" advantage has been that it was able to exterminate the indigenous population, forcibly drive out the Spanish and Russians, and colonize a huge landmass with everyone primarily using a single language. The language barrier between English and Spanish is far less than between Greek and German.
As far as what this means for bitcoin, I'm with P4man: less Euro play money to spend on novelties like btc.
However, if the Drachma makes a comeback, I'd expect Bitcoin to do well in the Greek zone as a hedge against devaluation of both the Euro and Drachma.
There's evidence that countries that have experienced overnight currency devaluations are more likely to take up bitcoins, such as Ukraine and Bulgaria:
(from http://www.thebitcointrader.com/2011_10_01_archive.html )
BTCurious, I think your best bet is to diversify diversity diversify. My thought would be 25% cash, 25% bank euro, 25% bank USD, 25% bitcoin. If one or two fail, you won't be wiped out, and if USD or BTC shoot up relative EUR, you might come out ahead.
But also, keep in mind that currency "failure" is a loose term: if EUR drops by 50% vs. USD, people will consider it to have "failed", but it will still be useful paper to own.