Since the end of World War II, the US has been a core variable in the European integration process. The transatlantic security community, or the Euro-Atlantic community, has contributed to providing a security umbrella over the European construction. In each phase of the integration process, either the European Defense Community or more recently, the CSDP, the US was directly and/or indirectly involved in it. Two factors shall be identified. First, American foreign policy does impact the European approach to foreign and security policy. The more recent pivot to Asia calls for greater European contribution to regional security. Second, the North Atlantic Treaty Organization (NATO) is an extension of US foreign policy and has contributed to European security since 1949. In order to understand the US approach to the European defense experiment, NATO has to be incorporated into the argument.