There's little question that the U.S. could legally have prosecuted Jane Fonda for treason -- see Dr. Hank Holzer's "Aid and Comfort" for a detailed layout of that legal case.
And America had the political will to engage in the military campaign when it began, and also for years thereafter, until it was eventually eroded by leftist opposition and the lack of tangible success.
If you're going to argue that the U.S. shouldn't engage in any military action that the people might later disapprove, that pretty well eliminates everything...
If I am a U.S. soldier doing a combat tour in Vietnam and I come home to find that some dip-sh!t who "gave aid and comfort to the enemy" was not prosecuted by the government that sent me over there in the first place, you can be sure that I'd be extremely p!ssed off -- more so at the f#ckers in my government than at the traitor herself.
At least in the American Revolution the colonials who waged the war had no illusions about their fellow country men. Tories who supported the British during the war were routinely burned out of their homes and chased to Canada or back to Britain.