"Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court."
Not that the US follows the constitution, but you know, in theory nothing he's done is remotely close to treason, and even if what he did qualifies, it might be difficult to get two Witnesses.