Treason can stick, but you cant get the death penalty for it except in wartime if I recall correctly. So, hopefully no, noone would be put to death for treason in an undeclared war... because if congress hasnt declared war, then legally and morally speaking we are not at war. Even though many like to pretend otherwise so they can do whatever the fuck they want.

For who could be free when every other man's humour might domineer over him? - John Locke (2nd Treatise, sect 57)