He is guilty of giving the documents to friendly press, not everybody. The press then revealed some of the exposed documents, but not all of them, and censored some information. This is different than Manning, who revealed the documents to a bulk dump leak site.
The real problem is the espionage charge, though. This is based on the loosely worded and likely unconstitutional Espionage Act of 1917, which states that giving Confidential information to anyone that "is not supposed to have it" is illegal. The White House itself has committed treason by this standard by revealing the name of the CIA top official in Afghanistan last week.
As long as the espionage charge stands, I don't think Snowden can get a fair trial in the US. With Obama backing the espionage charge, there is no way he gets pardoned. In fact, I'd say there is a better chance he gets hung than there is he gets a pardon, despite the government promise that they won't chase execution for the espionage charge.