Chu was arrested six years ago and charged with aiding and abetting terrorists in a plot to harm Americans. While he has been charged, he has not yet faced trial. Why would this be a Sixth Amendment case?

ok lets look at it. this is the sixth amendment: All criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the Assistance of Counsel for his defence.