As others have already said, the main difference is that the US has true political and social union to go with the financial union (if anyone is interested, this state of affairs came about during and in the aftermath of the American Civil War - indeed the war was only possible because until then the states really were independant entities capabable of defying the federal government - this is of course no longer the case).
To make it more concrete, when Louisiana has financial problems, the first remedy for Louisianans(???) is to move to another state. The next remedy is for the federal government to step in and inject funds into the economy, which is pretty much what they do, taking those funds from wealthy states such as New York and California. This works, because if the federal government hangs Louisiana out to dry, they will potentially lose seats, and potentially the presidency, come next election, so even though it annoys the rich states a little, the best political strategy is to provide as much financial support to Louisiana as possible without pissing off the rich states too much.
In Europe this is not the case. Indeed, this is precisely the problem that has been debated over recent weeks. The rich states (err, state, because Germany is about it at the moment, although I suppose you could count in the UK as well) refuses to pump more money into Greece's economy. They consider the situation to be Greece's problem, and they aren't going to do anything to help. Politically, there is no impact on German leaders to take this stance - or even worse, there is a political advantage to take this stance, as only Germans vote for German political leaders. Socially, with two very different cultures, and two different languages, there is not much by way of social cohesion. There are not huge numbers of mixed German / Greek families capable of looking across the border and seeing "us", not "them".
Imagine a European political structure that was truly integrated: There is a European president that commands the European military, and controls the European budget which comes directly from taxes that the European government levies on it's people, instead of the budget being made up from funds allocated to the European government by it's member state governments (which is the case today). In such a case, the European president would be much more willing to listen to Greece's case than the German Chancellor is today, and we wouldn't have this crisis.
That in a nutshell is the difference between the US and Europe. It has long been the UK's biggest criticism of the Euro, and is on record as being the reason they decided to not join the Eurozone (no financial union without political union).
To make it more concrete, when Louisiana has financial problems, the first remedy for Louisianans(???) is to move to another state. The next remedy is for the federal government to step in and inject funds into the economy, which is pretty much what they do, taking those funds from wealthy states such as New York and California. This works, because if the federal government hangs Louisiana out to dry, they will potentially lose seats, and potentially the presidency, come next election, so even though it annoys the rich states a little, the best political strategy is to provide as much financial support to Louisiana as possible without pissing off the rich states too much.
In Europe this is not the case. Indeed, this is precisely the problem that has been debated over recent weeks. The rich states (err, state, because Germany is about it at the moment, although I suppose you could count in the UK as well) refuses to pump more money into Greece's economy. They consider the situation to be Greece's problem, and they aren't going to do anything to help. Politically, there is no impact on German leaders to take this stance - or even worse, there is a political advantage to take this stance, as only Germans vote for German political leaders. Socially, with two very different cultures, and two different languages, there is not much by way of social cohesion. There are not huge numbers of mixed German / Greek families capable of looking across the border and seeing "us", not "them".
Imagine a European political structure that was truly integrated: There is a European president that commands the European military, and controls the European budget which comes directly from taxes that the European government levies on it's people, instead of the budget being made up from funds allocated to the European government by it's member state governments (which is the case today). In such a case, the European president would be much more willing to listen to Greece's case than the German Chancellor is today, and we wouldn't have this crisis.
That in a nutshell is the difference between the US and Europe. It has long been the UK's biggest criticism of the Euro, and is on record as being the reason they decided to not join the Eurozone (no financial union without political union).