Plus the $41 billion number is just an estimate; the real total won't be known until all the derivative contracts are unwound.
Either way, it would be a mistake to dismiss a Greek default as irrelevant to us.
Out of the 700 billion TARP fund, only 51 billion remains outstanding (as of September last year), which is larger then the 41 billion number you were floating around:
http://online.wsj.com/article/SB1000142405274870343160457552...
I'm not saying all banks will be fine if Greece "defaults" (remember in this case "defaulting" implies restructed debt), but causing a US recession? Highly highly unlikely.
But even according to the article you posted, bank balance sheets are still weak.
Losing $41 billion (or more, possibly, given the nature of these derivatives) is not going to be good news for them.
While technically not in recession, the economy is not thriving, either, and so one blow like this may indeed push it back into recession.