Yes, there are problems surrounding Greece with its dependence of the banking system on cheap ECB repo rates for Greek government debt. Unfortunately, with downgrades, those bonds are not eligible any more and this leads to the funding problem.
But the comparison to the US is puzzling me. California is struggeling severely to balance their budget and I would say that California to the US (and to the world) is more relevant than Greece to the EU. Bear in mind that California is the 7th largest economy on earth if it was a stand-alone. The market seems to be ignorant towards this argument.