Major sports leagues in the U.S.

I was going to make some research on the media side of the major sports leagues in the U.S. and present it using prezi.com. But it appeared that I had to gather basic information about the leagues first. Here is the link. First, I am talking about the whole ecosystem of the professional sports in the United States, then am covering every league highlighting its challenges and important points they deserve closer attention.
Next time I am going to work on my initial idea of covering the media aspect of the leagues.