Some perspective:
American power is not in decline. It is unparalleled, and it is increasing. The US economy is not only the largest in the world, it has no close competitor. Yes, China is the second largest economy, but that is a deceptive title. The Chinese economy is almost half the size of the US economy…we’re not talking about a close second here.
Furthermore, the Chinese economy is largely dependent on the US economy. It is thriving because it is a manufacturing hub for American companies producing goods for American consumers. China’s prosperity is entirely reliant upon US economic activity.
As a power, China is buying influence in various parts of the world, particularly in Africa, through financial aid and investment, offering developing countries an alternative to the International Monetary Fund and the World Bank. However, American military power can easily wreck this influence, that is a primary reason for the AFRICOM military program in Africa; in line with the strategic vision of Nato which defined China’s business involvement in Africa as “rogue aid” and “weapons of finance” undertaken to threaten American interests.
Russia, which is sometimes fancifully offered as a power competitor to the United States, is barely in the top ten global economies. Russia intervened in Syria precisely because it is becoming so isolated that it has very little influence left in the region.
Indeed, Russia is losing influence within its own region. Georgia is integrating into the West, Azerbaijan is defying Moscow over the Nagorno-Karabakh conflict, and, of course, Russia’s annexation of Crimea has created European antagonism. Turkey has also not hesitated to assert its authority against Russian provocation. It is a country in decline, not ascendancy. It is becoming more isolated, not more influential.
Now, having said that, yes, American power is still dominant and unrivalled, however, American power is not,strictly speaking, American anymore. It is an instrument of multinational corporate power which has no nationalistic loyalties. American power does not serve American interests; it is mobilised to protect and advance the interests of corporations…or more specifically, the interests of the super-rich. That most of the world’s richest people are American is the only nationalistic element in the equation.
So, America as a nation is in decline; but as a power, it remains unchallenged.