With big US bank stocks again sliding, investors are wondering how much is due to Europe's woes versus blowback from JP Morgan Chase's trading debacle. One answer: the issues are intertwined.

When JP Morgan revealed $2bn-plus in trading losses, it said it had executed hedges poorly and failed to monitor them properly. This raised questions about JP Morgan's overall hedging abilities, including those meant to offset exposures to Europe. And, if JP Morgan could mess up, what about Citigroup, Bank of America, Morgan Stanley or Goldman Sachs?