There is an important debate among foreign policy theorists and practitioners regarding the most effective way to protect and promote U.S. national security interests in the 21st century. It involves four general approaches to the world: (1) retrenchment, (2) offshore balancing, (3) liberal internationalism, and (4) conservative internationalism. Each of these theories or approaches is based on a broad worldview about America's proper role in the world. All of them are based in part on classical geopolitics.
Retrenchment and offshore balancing envision a more modest use of American power, frequently decrying "imperial overstretch," and favoring a more nuanced and multilateral approach to international disputes.
The Obama administration, in the wake of two unresolved and increasingly unpopular wars in Afghanistan and Iraq, and with a more benign view of the intentions of America's potential adversaries, practiced retrenchment across the globe. It largely withdrew U.S. military power from Iraq. It signaled a lack of U.S. resolve in Afghanistan. It "led from behind" in Libya. It stood by as Russia reasserted itself in the Eastern Europe and the Middle East, and China moved aggressively in the South China Sea. It scaled-back the Global War on Terror.
Obama's foreign policy was an attempt at a return to "normalcy" and a retreat from world leadership reminiscent of the Harding-Coolidge administrations after World
War I, and with similar consequences, i.e., other powers--Russia, China, Iran, and ISIS--became more assertive on the world stage.
Advocates of offshore balancing--most prominently John Mearsheimer and Stephen Walt--criticize the overextension of American power since the end of the Cold War, preferring instead that the U.S. husband its power and use it only when necessary to redress a global imbalance of power that threatens core U.S. interests. They view America as the successor to the British Empire, which for centuries threw its weight on the scales of power to defeat whatever continental power threatened to upset the global power balance.
Advocates of liberal internationalism and conservative internationalism want the United States to continue to shape the international order that has been in place since the end of World War II. America's forward presence in Western Europe, the Middle East and East Asia, they believe, is essential to promoting U.S. interest abroad and to preventing the rise of a new peer competitor.