Short answer: we don’t have to be screwed, but probably are.
There will probably be another recession if Greece defaults, and who knows how leaving the euro would go? Worst case scenario is they default, leave, print their own money, blah blah, and the banking system is in shambles. Better case other EU powers help them transition to their own currency, smoothly as possible. One problem is, smoothly as possible isn’t very smooth. Whatever happens, holders of Greek euro-denominated securities are going to want to dump those before the new currency starts floating against the euro while holders of euro-denominated securities in every other EU country will want to do likewise to some extent. And things don’t go very well when an entire country’s securities (stocks, bonds, etc.) all get dumped. It probably annoys the Protestants, but the best case for, well, the whole planet is bailing them out and maybe avoiding a recession. What really should be done is a longer-term plan that fixes Greece and finds ways to assure this doesn’t afflict the eurozone again.
And @ETpro is probably right about the Republikans, though perhaps Europeans are at least sharp enough to see that not bailing out Greece could help encourage Obama to lose, which would be awful for economies on both sides of the Atlantic. Well, we’ll see. Sarkozy is gone, but Merkel is somewhat like a Republikan on foreign affairs, but is somewhat more traditional conservative on domestic matters – what that means is, the swarthies in the south of Europe get something more akin to what Americans call conservatism, and Germany gets a more traditional conservatism that preserves a functioning welfare state married to a healthy-ish market economy. Then again, she may not want to be massaged by complete dumbass – this one wearing creepy magic underwear.