Benedict Arnold was a traitor, but was never tried as one. He switched sides twice during the revolutionary war. 

Benedict ArnoldBy Thomas Hart -
https://commons.wikimedia.org/w/index.php

Aaron Burr was never a traitor, but he was tried and acquitted. That case, the United States v. Aaron Burr, is still precedent today. It maintains the very narrow constitutional definition of treason.

The definition of a traitor cannot be changed by case law or statute. Instead, it is found directly in Article Three, Section 3 of the constitution. However, if you are not a lawyer or a newly sworn in naturalized citizen of the United States, there is a big chance that you may not know this. One of the ironies of the American experience is that those born into it are often ignorant of the history.