Just a thought, inspired by dinner last night with a "public diplomacy" official who asserted that because the world mourned for Michael Jackson, it indicated that the world was looking to America for leadership rather than, for example, China.
Someone I know at the dinner suggested that, to the contrary, cultural influence follows on the heels of economic, political, and military power--that culture, especially pop culture, is a lagging rather than leading indicator. Which means that countries with a low profile culturally--for example, again, China--would become culturally dominant globally after achieving primacy in other spheres. The argument is simple. French became the language of diplomacy in the 19th Century not only because of the appeal of French artists, writers, and composers, but because Napoleon had conquered most of Europe. To understand and communicate with the French, one needed to know French. After the Franco-Prussian War, with the rise of German military and scientific might, German became the culture to know, and everything from Beethoven to Thomas Mann to Richard Wagner to goose-stepping soldiers de rigueur. Viz., Christopher Isherwood's Berlin Stories. With the crushing of Germany in World War II, English came to replace French as the language of diplomacy and German as the language of science. Widepread Anglophilia was a reflection of the fact that the sun never set on the British Empire. With the collapse of that Empire and assumption of the mantle by the USA, dressing for dinner and memorizing Keats and Shelley were abandoned in favor of blue jeans, country-western music, and Michael Jackson. Likewise one may chart the rise and fall of interest in Russian culture according to the ups and downs of the Cold War.
In this model of cultural dominance, the spread of a particular cultural icon's image around the world is dependent on base of military, economic, and political supremacy.
In sum, the continuing spread of American culture, and indeed American values, depends upon military victory, economic prosperity, and political dynamism. To the extent to which other nations are victorious, prosperous, and dynamic, their cultural influences should follow.