>>2612163basically, the euro prevents exchange rates from adjusting to any single national economy (so, if, say, germany is running a trade surplus and france is running a trade deficit, the value of the euro stays stable when what it really ought to do is drop in france and increase in germany to restore balance. since this can't happen through currency value changing, the main option left is "internal devaluation" - e.g. painful wage and welfare cuts combined with unemployment until competitiveness improves in france.), prevents monetary policy from adjusting to any specific national economy - though in practice set for germany - (so if france is in recession while germany is booming, the ECB has to decide between high inflation in germany to help with france's recession, or worsening france's recession to cool the german economy), but it does not mandate large-scale fiscal transfers between france and germany (which is how the US solves this problem. its states are nearly as diverse as Europe's, but the federal government takes money from California and throws it at Alabama.)
all of these are compounded by the fact that national governments - entirely responsible for fiscal policy - borrow in a currency controlled by the ECB, not by themselves. the greek debt crisis is impossible for a country that controls and borrows in its own currency. if (say) britain got into the same problem, the central bank could always just print pounds. greece can't do that because the ECB owns the money printer instead of the greek central bank, so it's forced to do what the other eurozone countries demand in exchange for loans.
(this also arises in cases like latin american countries who used the money printer so often that lenders will now only lend to them in USD, but it's bizarre that these conditions are imposed across europe on countries that were once basically trusted to run their own affairs.)
basically: it is not that a European confederation is itself a fundamentally bad idea, it is that the specific institutions of monetary union without fiscal union are flawed. most bourgeois economists knew this in advance but it went ahead anyway because it was a political project. (ironically, one primarily demanded by France under the utterly wrongheaded idea it would
constrain a unified Germany from dominating Europe through a strong deutschmark.)