I don't think it's as adverserial as it may look. The US dollar is still the reserve currency, and as such, a quick demise without a replacement would be traumatic for the global economy. Everyone loses initially. Thus, the Euro is singled out for now to deflect attention of the dollar - but keep in mind, who will be writing a good deal of the checks for the Euroland bailouts as they come due? The IMF with significant US backing, that's who. Looks to me like a quid pro quo, despite the inherent conflicts between the US and EU.
Default may not be the issue, but rising cost of capital is hard to deny. Obviously has bearing on existing debt on all points of their yield curve and, perhaps more importantly, ........................ future funding.
When I saw that happen it was then I started buying Greek Bank Call Options... Not crazy enough to buy stocks. The banks would be punished to the point of no return and there is no way that the ECB and Euroland would let Greece go under. Of course everybody will get their pound of Greek flesh... The Greek knows that they have no choice and will go along.