I must dispute Paul Fussell’s assertions in his November 1989 interview (“The Real War”) that the Vietnam War would probably still be going on if Congress had declared war, that a declaration of war makes dissent treason, that a declaration of war guarantees public support, and that the Founding Fathers gave Congress the power to declare war to ensure public support for wars.
A declaration of war by Congress does not guarantee public support for a war. Consider the widespread opposition to the War of 1812 and the war with Mexico. In the 1812 presidential election DeWitt Clinton ran against Madison on an antiwar platform and he and his supporters were not prosecuted for treason. Nowhere in the debates at the Constitutional Convention and in the lively campaign to ratify the Constitution was the requirement that Congress declare war touted as a means of making wars easier to conduct by guaranteeing public support and suppressing dissent. Indeed, during the ratification controversy it was widely feared that the federal government could use a state of war to suppress opposition.
The definition of treason in the Constitution (the only crime therein defined) is deliberately narrow, requiring that treason be an overt act and not merely dissent. The First Amendment says nothing about freedom of expression automatically becoming restricted by a congressional act of war.