US-EU relations regarding European defense integration has passed several milestones since the 1990s when the West first faced serious challenges in Europe after the end of the Cold War. The military conflicts in the Balkans, resulting from Yugoslavia’s break-up gave momentum to the integration process in the European Union. Profound changes in international environment are making the United States reconsider its views on the defense integration unfolding in the EU. Placing more responsibilities on the European Union in the security area entails the necessity for Washington to overcome entrenched prejudices, as well as suspicions that the EU ambitions may pose risks and challenges to NATO coherence. Increased EU activities in shaping European military-industrial policy and in providing large-scale supplies of weapons and ammunitions to Ukraine are leading the United States to take a fresh look at the process of European defense integration.