Since the Soviet Union collapsed in 1991, the U.S. has been the undisputed global superpower. It’s difficult to overstate how important and unprecedented the Soviet collapse was to the global balance of power. For the first time in 500 years, no single European power dominated the world. For the first time in history, the world’s center of gravity was in the Western Hemisphere. One of the areas where U.S. dominance is most visible is its military strength. The U.S. spends more than the next 10 countries combined on its military forces. This is in part a reflection of its economic strength – the U.S. represents nearly a quarter of the global economy.
Still, the United States isn’t omnipotent. Its power, like all power, has limits, and the scope of U.S. foreign policy has begun to outstrip even the tremendous resources of the United States. It identified China and Russia as long-term competitors for global power and sought to isolate them through a combination of sanctions, tariffs and other economic instruments. It also identified Iran and North Korea as potential threats to its allies in the Middle East and East Asia and has committed substantial resources to constraining both. The U.S. remains at war in the Muslim world, though it plans to withdraw from Syria in the coming months and pull thousands of troops out of Afghanistan. So despite surpassing all other nations in military spending by far, the U.S. is increasingly reliant on its allies to help manage conflicts and challenges abroad.