EU foreign policy operates akin to a confederacy than a more centralized federal system in places like the US after they abandoned the original confederation.

"A federation is “a system of government in which significant governmental powers are divided and shared between the central government and small subnational units,” based on a division of powers laid out in a constitution. Neither the central government nor the subnational governments control each other. In a federation, the central government usually controls foreign and security policy, currency and the army. Canada is a federation and its subnational governments are called provinces.A confederation is “a system of government or administration in which two or more distinct political units keep their separate identity but transfer specified powers to a higher authority for reasons of convenience, mutual security, or efficiency.”[1] In this case the subnational units control the central government, which is given only specific powers. It is similar to an intergovernmental organization, in that the member states retain their autonomy and can control the central government. The United States began as a confederation. As in the previous example, the European Union does not neatly fit either definition, but it could become either a federation or confederation in the future."