The United States was once the Julius Caesar of the world's economies. Like Caesar in his Rome, what America said and did became the standard and the rule for the non-Stalinist nations who emulated everything in their effort to be as prosperous as we became. As for the Stalinist nations, they were undermined as much by Levi's jeans and rock'n'roll as they were by the huge and very hostile American military presense, which by design surrounded them in ways for which Hitler would have sold his sorry soul many times over.
But as the Stalinist nations collapsed, and Glasnost and Perestroika replaced "global revolution" and "the dictatorship of the proletariat", there was no longer any opponent to use to motivate the capitalist working class to strive for efficiency and greater productivity. Those potential rivals since held up to replace Stalinism — Muslim extremists and Mexican immigrants — have neither wealth, power, nor any great economic output useful for frightful comparison. Without any such rival, the forces which feed on unbridaled competition required a focus, and it was upon its own that these forces were directed.
America entered this period of economic dominance due to the ravages of war unleashed upon all of the other major industrial nations. The growth of American economic power was an opportunity of historic proportions. But to maintain that power, it was required that no other economy be allowed to achieve parity. One way to block this development would have been to go to war to destroy any nascent rival, as has been done repeatedly throughout written history, and very likely before. But the destruction committed during WWII by all sides demonstrated that the potential to end human life on this planet existed, and atomic weaponry was not the only reason this could occur. Thus following this path was not encouraged.
The other way to prevent rivalries from developing is to subvert them as they grow. After WWII, the world was in perfect condition for the only undamaged industrial economy to direct and control the restoration of the rest of the world so that no such contest could develop. The Marshall Plan — while it did a lot of good for the average European — was the means by which American firms could gain control of ravaged rivals, and which would then be in position to "influence" local governments to see things in certain ways critical to American hegemony. It also helped that their militaries were largely ceremonial, with the heavy defensive lifting being performed by American forces, which still remain in de facto occupation of the former Axis nations today.
This plan worked as long as those who greatly benefitted from this system continued to reinvest in the American worker who made all of this possible. But once it was clear that Stalinism was too stressed to survive much longer, and that there was no convenient enemy waiting on the sidelines, one had to be created. That enemy was the very workforce which created the prosperity enjoyed by the entire nation. Our usefulness to the elites had come to an end, and to protect their blood-stained profits, we had to go.