I was reminded of the extreme contagion factor of many products of American culture. For what its worth, here's my theory of why that is so. As an immigrant nation, we have been exposed to elements of cultures from all over the world. In our market economy, consumers with varied backgrounds "vote" with their dollars for the most popular of these.
Neapolitan pizza became American, so did tacos and a hundred other trends. And Hollywood helped us sell them to the world, lip-synced in the local language.
But the reason American fads catch on around the world faster than, say, French fads or Korean fads, is because our fads have to succeed in a multicultural market. Things that appeal to people of the many different backgrounds found here are likely to be well-received around the world.