Oh, really?
I must have missed something.
Can you educate me by showing me where the US Congress declared war on Vietnam?
If they didn't, it would have been an illegal war, and I am sure our government would never do anything illegal.
• August 1964: The attacks in the Gulf of Tonkin spur Congress to pass the Gulf of Tonkin Resolution, which authorizes the president to “take all necessary measures, including the use of armed force” against any aggressor in the conflict
So technically our leaders never followed the Constitution nor the Supreme Court ruling about Lincoln attacking the South without Congress approval when it came to Vietnam to Declare War. Unfortunately we lost 58,000 troops in that “measures”.
Please read the following site, suits were filed over the “Vietnam measures” but the Supreme Court refused to consider the issue in any of the forms in which it was presented.
So the powers to be just did not have Congress declare war and the Supreme Court did not take up the cases which resulted from that failure. The Checks and Balances failed and the Court refused to review, they just thumbed their nose at us!
https://www.law.cornell.edu/constitution-conan/article-1/section-8/clause-11/power-to-declare-war