Considering the Iraq crisis in 2003, it is legitimate to ask oneself whether NATO is still an alliance, in the classical meaning of the word. The Bush Administration has favored a one-time coalition over the traditional Atlantic alliance. Yet the Iraqi case only revealed a progressive evolution of the American standpoint on NATO, since the failed interventions in Kosovo, and including the rejection of the help NATO offered in the aftermath of September 11th. Using a historical reminder, the author of this paper analyses the evolution of the American thinking on alliances in order to understand why the United States are turning away from the Atlantic military conceptions. This understanding effort may allow Europe to suggest an alternative evolution of the transatlantic organization by integrating the coalition principle and to be freed, in their turn, from constraints inherited from the Cold War. – Summary AFRI-2005