[jcranmer]

No one has been convicted of treason since WWII. One person has been charged with treason, but they were remote-murdered by the US government before they were tried, and it's not at all clear that a conviction would have withstood appeal. Note that Congress did expressly pass a resolution in the Global War on Terror that can be construed as declaring war on terrorists; if anything short of outright declaration of war qualifies as a foreign entity as an "enemy" for the purposes of the treason declaration, that is it.