England had a lot of colonies around in the whole world and this is one reason why English is such a big language. I also think that the industrial revulsion was a big factor. The USA were one of the winners of World War 2. I also think this has something to do with the English language and that the language went bigger.
http://globalvillage.intuto.com/cats/content.aspx?courseID=1051&learningID=10447
Sources:
https://www.youtube.com/watch?v=SfKhlJIAhew
https://www.youtube.com/watch?v=-YDGxVNuxO0