I have trouble believing this is serious.
Now, don't get me wrong. I don't like Obama, and I also think this teenager sounds like kind of an ass. "It's the sort of thing teenagers do" doesn't sound like a very sincere or well-considered excuse, coming from not only a teenager, but the one whose action is in question.
Maybe he threatened the president (apparently he was 'drunk' and forgot what he actually wrote). But being banned from the US over insulting the president in an email? That just doesn't seem realistic.
On the other hand, maybe he called Obama a pig instead of a prick. Then the banning would make sense, because that's a pretty grave insult to a muslim.