Is America overstretched? The question is central to the entire decline debate. After seven decades of global predominance, in World War II, Cold War, post–Cold War, and post-9/11 eras, have the burdens become more than the United States is able – or willing – to bear? As discussed in Chapter 2, the wars in Iraq and Afghanistan, the financial crisis and great recession, an aging population with its costly entitlement programs, and the weight of debt and deficit call into question America's capacity to play its accustomed international role.

This is not only a matter of resources, but also of profound changes in world affairs. Globalization, the rise of China and other emerging powers, popular revolts against long-entrenched Arab despots, erosion in the capability of America’s traditional allies, and the dangers posed by terrorism, radical Islamism, nuclear proliferation, and failing or failed states shape a world very different from the one in which the Cold War came to an end little more than two decades ago.