The North Atlantic Treaty Organization, bringing the US and Western Europe into an alliance against the Soviet Union, was established by President Truman in 1949.

Designed to bolster European postwar recovery in the hope that military security would reinforce aid given in the Marshall Plan, the organization also increased American visibility and influence in the region. A product of the growing antagonism between the US and the Soviet Union, and European fears of the latter, the establishment of NATO further escalated Cold War animosities and led the Soviets to create the Warsaw Pact.

The end of the Cold War has transformed NATO. Pushed by Secretary of State Madeleine Albright, NATO has incorporated a number of former Warsaw Pact nations (Poland, Hungary and the Czech Republic). It has also altered its relationship with Russia, though Russia still views NATO, backed by the US, as encroaching on its allies and Russian internal affairs. Thus far, NATO has opted to keep the Russians out of the organization, but has endeavored to coordinate policy with its erstwhile foe. Lastly NATO has begun to expand its mission from containment of a particular nation to that of regional policing. In the Balkans, it took the lead in pushing for negotiations between warring groups and in the 1999 military intervention against the Serbs in Kosovo.

During the Clinton administration, a rift between the US and its NATO partners grew.

An increasingly consolidated European Community has tried to limit American leadership, particularly as Americans express their reluctance to commit troops to conflicts that have little strategic importance to the US. In addition, the existence of large US military bases across Europe no longer seems warranted; some have been returned to the host nations. A growing impatience towards the American soldiers and their families near such bases is now evident, especially with scuffles between locals and American soldiers and their families.