The paper aims at revisiting the causality of European integration with a counterfactual methodology. It argues that European regionalization stems from international structures. The puzzle comes from a simple observation: European dynamics have not been enough to lead to integration and would have failed without an international impetus. Based on these non-occurred opportunities –meaning blockages and failures -, the methodology of counterfactual history has shed light on three main hypotheses. From 1945 up to the 1960s, the US structural power - with its three dimensions: production, currency and defense (Strange, 1988) - laid the foundations for the internal market. From the 1960s, when the US lost their production and monetary structural power, transatlantic economic competition encouraged the deepening of the internal market and the implementation of secondary economic policies. Finally, the end of the Cold War, the change of US military structural power and the political competition with the US allowed for the development of a European political union, altogether with Home affairs and foreign policies as well as the last waves of enlargement. This theoretical framework seems to work for current events (Brexit, revival of the defense policy), even if we still lack of critical distance.
