From ‘The Grand Chessboard’ (1997) by Zbigniew Brzezinski,

*The political momentum for Europe’s unification was once driven by three main impulses: the memories of the destructive two world wars, the desire for economic recovery, and the insecurity generated by the Soviet threat. By the mid-nineties, however, these impulses had faded. Economic recovery by and large has been achieved; if anything, the problem Europe increasingly faces is that of an excessively burdensome welfare system that is sapping its economic vitality, while the passionate resistance to any reform by special interests is diverting European political attention inward. *

“An excessively burdensome welfare system” is probably the root cause of the current debt crisis in eurozone