The original question had to be edited. One reason that American culture dominated the Post- World War II world existed in the limited number of options available. With the conclusion of the Second World War, there were only two cultural options available. The United States and the Soviet Union remained as the two viable world cultural options. The rest of Europe had been shattered by the war. Nations in Africa, Asia, and South America were only coming to a point where they would be awoken. Japan was decimated with two atomic bombs. In the end, American culture ended up dominating the world stage because, frankly, there were not many other options.
In this reason exists another factor behind why American culture dominated the world after World War II. So many nations sought to determine what their identity would be in a post- World War II world. The competing images of cultural identity being offered were the individuality, prosperity, and material advancement of American culture as opposed to the homogeneous collectivization of the Russian vision of culture. For nations seeking to define which vision was more appealing, American culture dominated the world because it was more exportable.
There were elements of American culture that appealed to more people around the world than elements of the Soviet culture. For example, American cultural icons such as Elvis Presley, Rock and Roll music, and dances along with Marilyn Monroe and Hollywood films were more appealing around the world than anything that the Russians were offering. The emergence of television in America enabled cultural notions of American identity beamed all over the globe. More nations wanted to be the vision of culture that America offered more than the vision that the Soviets were offering. This became another reason why American culture dominated the post- World War II world.