The paper investigates the reasons and consequences of the EU’s intergovernmental transformation under the impact of the euro crisis through the ‘most similar cases’ strategy. Based on the analytical distinction between federal states and federal unions, the paper assumes that the EU belongs to the latter case. Federal states derive from the disaggregation of a previous unitary state, whereas federal unions from the aggregation of previously independent states. Among established democracies, the two main cases of federal unions are the US and Switzerland (and partially Canada that combined both processes). Under the impact of the crisis, the outcome has been the blurring of the distinction between member states and the Union and the formation of hierarchical relations within the intergovernmental institutions. Comparison with how the other federal unions answer to the financial crisis, those consequences are predictable when a process of aggregation is not ordered by an agreed federal document.
