It's a lot of things, but Constitutionally it's not treason, which is very specifically defined in the Constitution itself:
Article III, Section. 3.
Treason against the United States shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort.
Of course, he's arguably done that, the adhering and giving aid and comfort bit, as well.
There's minor dispute between a white cop and a black proffessor, and right a way "The Cop Acted Stupidly", but let a muzzi kill 14 (including an unborn child) on a US military base, about 3 miles from where I sit in fact, and "we must not jump to conclusions" Nor did his hand picked "commission" even mention "muslim" or "islam" in their report on the matter. That's pretty much given aide and comfort, and adhering, to the enemies of the United States.