If you advocate deliberately aiding the enemy, or any action whose purpose is to cause the defeat of the US, or disclose classified information to the enemy, either directly or via third parties, then yes. The Constitutional definition of treason is very specific and clear:
Originally Posted by Wei Wu Wei
Treason against the United States, shall consist only in levying war against them, or in adhering to their enemies, giving them aid and comfort. No person shall be convicted of treason unless on the testimony of two witnesses to the same overt act, or on confession in open court.
The Congress shall have power to declare the punishment of treason, but no attainder of treason shall work corruption of blood, or forfeiture except during the life of the person attainted
Example 1: A sign that says, "We support our troops when they kill their officers" is an open exhortation to mutiny, and if done so for the purpose of ensuring American defeat, constitutes "levying war against them, or in adhering to their enemies, giving them aid and comfort."
Example 2: The statements by various imams that American Muslims' duty is to kill Americans for Allah (acted on by MAJ Nidal Hasan, among others), are treason exhortations to "levying war against them."
Example 3: Code Pink soliciting funds to provide to Iraqi insurgents clearly constitutes "giving them aid and comfort."
Example 4: Waving the enemy's flag in public is an announcement of solidarity with the enemy and loyalty to that enemy or, as the Constitution puts it, "adhering to their enemies."