Why are international news networks in the USA e.g CNN,USA providing a limited array of stories?

I was shocked when i was in the US to discover that news in the USA does not give a true picture of what is happening in the world like the way BBC and Al Jazeera and to a limited degree CNN (international) do. May be it explains why the majority of Americans actually believed that Saddam Hussein was responsible for 9/11 yet the rest of the world knew otherwise.