America First? Isolationism in U.S. Foreign Policy from the 19th to the 21st Century

During the 2016 election campaign, President Donald J. Trump championed a policy of intervention and isolation in U.S. foreign policy, which aroused fears among European North Atlantic Treaty Organization (NATO) allies about U.S. commitments to collective defense. This contentious issue points to a preference in certain political circles for an end to U.S. interventionism, which, from a foreign policy perspective, seems tantamount to isolationism. This thesis examines isolationism in the experience of statecraft and considers the potential implications of this nations deeply rooted isolationist tendencies for continued U.S. security commitments to NATO. To trace the evolution of isolationism, this thesis analyzes case studies of U.S. decision-making prior to entering the First and Second World Wars, U.S. involvement in NATO after the Second World War, and resistance within the Senate to large numbers of U.S. troops in Europe in the 1960s and 1970s. The analysis includes consideration of congressional partisanship, public opinion, and domestic political issues in the shaping of U.S. foreign policy. This thesis concludes that domestic political issues dominate the conduct of U.S. foreign policy. The political agenda of the 2016 Trump campaign, as well as the first days of the administration, mirrored debates of the past, which should not surprise experts of U.S. political history.