I don't think Snowden actually gave the classified documents to China and Russia. He claims, and I recognize the face value that we can place on that, that he did not bring them to Russia and that he encrypted them in a way that he could not access them in Hong Kong.
Now he did provide them to journalists, and it's quite possible that China and Russia was able to take them from their computers. It's also quite possible that China and Russia had the files before Snowden took them, because of deeper security concerns.
Here is a good analysis of this:
I believe that both China and Russia had access to all the files that Snowden took well before Snowden took them.
www.wired.com
Even the worst case scenario though, that Snowden gave files to journalists who were not equipped to hold them, I think that is categorically different than explicitly offering them to foreign advisories.
I think there is also the point of what Snowden was producing: unconstitutional actions the government was taking on citizens. If one views treason as actions against the people of the United States, the government's actions could themselves be considered treasonous in this example. If treason is defined as actions taken against the government, however, than Snowden certainly fits that bill. That being said, I'm not going to defend every claim of "treason!" and "traitor" suggested by the fine folks of the forum.