The financial markets seem to typically "sell first", ask questions later. Yes, Greece is in trouble, (nothing new, we knew this since a few months ago). And yes, maybe even Spain and Portugal might be in trouble.
How would this derail U.S. economic recovery? Below article mentioned that U.S. exports to the WHOLE of Europe only constitutes 2% of U.S. GDP. Thus, from this Big Picture analysis, whatever happens to Greece, Spain and/or Portugal is NOT likely to have a big impact on U.S. economy, and thus unlikely to affect the World significantly.
Since U.S. economy constitutes 24% of the Global Economy, if U.S. is OK, the world will be ok. Despite so much talk about China and India, they currently only contributes to 7% and 2% of the Global economy respectively.