Yes.
Do you believe that the enemies of the United States are not comforted by the words and actions of the Dixie Chicks? Do you believe that the Dixie Chicks have not, by their actions, aided (and even emboldened) our enemies?
Please, I'd like to hear your explanation.
While am not an expert on the Constitution, I do not believe speaking against the war or in this case against the President constitutes either aid or comfort. Clearly, they are not levying war again the United States. And I would argue that giving them aid and comfort describes what adhering to their enemies means. I believe that it is talking about material aid and comfort, not moral support. In addition I doubt that our enemies care what the Dixie Chicks say or think.
That being said I think it was a stupid thing to say, I find it offensive, and am glad there is backlash. Treason is an extremely serious charge, not everyone who disagrees with the position of the United States (even if we take as a fact the United States is correct) is guilty of treason.