Adherents of the idea that the power of the United States will decline point to the fact that historically, all great powers have risen and fallen. The Roman Empire, Spain and Portugal in the 16th century, the Netherlands in the 17th century, France under the Emperor Napoleon at the end of the 18th century, the British Empire in the 19th and 20th centuries, the Russian Empire and later the Soviet Union: each rose and fell. During the Cold War the Americans had to share their power, but the fall of the Soviet Union in 1991 marked the beginning of a unique period in world history in which one country rose to an unassailable position of power and could in effect define the world order.

Some academics link the discussion about the decline of American power with the notion of ‘imperial overstretch’: the idea that the increasing economic and military costs of holding an empire together or expanding it become so massive that a great power falls. The British historian Paul Kennedy became famous for this theory. His book, The Rise and Fall of the Great Powers (1987), charts the rise and fall of global empires between 1500 and 1980. In the book he defends the argument that having access to raw materials and a long-lasting, strong economy determines a country's great power status. This is consistent with the modern debate about geo-economics. According to Kennedy, countries decline as great powers if they assume more economic and military commitments than they can handle. Kennedy thus argues that military might and economic development go hand in hand. In Kennedy's opinion, in most cases the fall of a great power is the result of protected, large-scale military deployment and neglect of the economy at times of war, and of the extent of the great power's relative decline in the decades preceding its ultimate fall.

Historically, hegemonic powers have spent more than 10 per cent of their GDP on defence. The figure for the United States is much lower. The Americans have undoubtedly spent astronomical sums on defence, but even at the peak of the wars in Iraq and Afghanistan, this never exceeded 4 per cent of GDP.