Hi Chris, a few words:
There is no proof as yet that Osama bin Laden was behind this attack. The full background, including events of 15 years ago, may come out, in background stories, if it turns out that he was, in fact, the mastermind of this attack.
Americans hate history. Events from 15 years ago may not seem relevant. The mainstream media has its political biases, but its primary bias is to make money, and it does that by being entertaining.
If the media did emphasize the historical connection, so what? Old allies sometimes become enemies. The Soviet Union was our ally during WWII, we poured aid of every kind into that country. Afterwards, it was our enemy. So? Things change.
Lawrence