Arnold Kling has a concise summary of the current crisis:
Apparently, the resolution of the debt ceiling restored the dollar’s status as a safe haven in the eyes of the world’s investors. That accelerated the flight from European sovereign debt and European banks. That in turn raised fears in financial markets, driving down stocks, including in the United States.
The European monetary system appears to suffer from the same problems as Bretton Woods.
European voters seem unlikely to tolerate the measures needed to maintain the current system. Yet the breakup will cause enough problems for the banking system that politicians will postpone it as long as possible.