Hey everyone, I'm a long time lurker but politics tends to get my blood boiling so I decided to come out of the shadows to put my two cents in.

A couple things need clarification:
1) As others have mentioned, you can't commit treason against a country that is not your own.
2) There have been fewer then 40 cases if treason in the united states in its history and very few of them convictions. As such, there is a very low possibility that any charges will be filed, let alone anyone being convicted of it.
3) Julian Assange (apart from being Australian) isn't the founder, owner, or the person who personally leaked this information. He's simply the spokesperson for Wikileaks and on their advisory board.
4) The information leaked is not only old, but they very specifically didn't release about 15000 documents that actually WERE a security risk. Yes, I'm basing that on something Wikileaks has said but they've made similar claims before and have proven them. As such, I have no reason to doubt it. Rather then repeat what the pundits are saying, I'd like anyone to point out specific reports from the leak that hurt either soldiers currently on the ground or civilian informants. If someone can, I'd be happy to admit I'm wrong.
The reason the US government is having a fit over this is because it makes them look bad. These reports paint the efforts in Afghanistan in a very different light then what is officially released and paraded through the mainstream media. This might hurt the war effort but not because it puts anyone in danger: It might hurt the war effort because it could lose what little popular support it had. To use a parallel: The Vietnam War.
One of the reasons that the Vietnam war was so horribly un-popular was the fact the war was covered in depth by the media. In previous wars, all that reached the general public were radio broadcasts (highly controlled and non-visual), government released statements, and (highly sanitized) pictures. For example, most of the truly graphic pictures from WW2 didn't come out until well after the war. Vietnam, however, not only had extensive coverage while the war was going on by independent (read as "Non-Government") sources but the coverage was highly critical of the war as a whole. This painted a VERY different picture then the one that was being officially released. Not only were there uncensored photographs being released, but television coverage that showed the american people the true horrors of the war. Many agree that one of the deciding factors in the Vietnam War was the press coverage. If it weren't for the media covering the My Lai Massacre, the Tet offensive, the bombing of Cambodia, and the release of the Pentagon papers, we probably would have been in that war a LOT longer and/or sent in far more troops.
However, as a caveat to the above, I have to say that I really don't expect anything to come of these leaked documents. The information is too old to cause any noticeable (military) effect and the american public has (at best) a short attention span for anything they don't like. Of course the politicians will rant and rave, the pundits will rand and rave, but in the end very little will change.
PS. After reading over what I just typed, I can just tell I'm going to be making a LOT of friends around here. /sarcasm.