War powers are probably ok as long as it's not a false flag operation. The Gulf of Tonkin and Iraqi WMD threats were based on complete bullshit.
Now what about all the ridiculous anti-communist rhetoric and the domino affect? Well, no change to war powers will cure stupidity.
Well, how do you suggest we separate 'BS' from 'non-BS'?
LBJ had his military reports that only much later turned out to not look like a trigger for war. Bottom line, running our destroyers around North Vietnamese waters (I mean, definitely international waters) escorting US-trained Souther Vietnamese terrorists in their territory (I mean minding their own business) were pretty much going to result in some conflict.
If it hadn't been WMD, it'd have been something else - they did cite a variety of justifications, they could have manufactured more (give the Kurds some arms and get them to attack Saddam, monitor Saddam's killing his own people in response). To this day I'm not sure the truth of the original Gulf War has come out, where Ambassador Gillespie was sort of asked by Saddam about invading Kuwait and told it not a concern to the US, only to then be used to justify war (completely with lies to Congress about the horror of the invasion, if you remember the Kuwaiti's daughter pretending to be a hospital worker who watched babies taken from incuabtors, reading a script in a campaign of lies created working with an ad agency office headed by Bush's former chief of staff).
These pretenses can be manufactured. If the government HAD used Operation Northwoods, it'd probably have worked - it's a lot fast to demand an immediate response to Castro's attack on the US than it is for anyone to sort out that it was actually a false flag attack.
I've written before about the power of claiming 'the other side started it', even under dubious circumstances or provoked attacks.
This goes all the way back, to the shot heard 'round the world that started our revolutionary war - the incident that started it was that rebellious colonists had a weapons stash that was illegal, British forces came to seize it, rebels learned well in advance and moved the stash, but waited for the British to arrive and shot at them 'defending' themselves from British attack.
Clearly, like most of these triggers for war, not itself a justification for war, just a trigger.
For our war with Mexico where we took half of their territory, our President simply announced the border had changed to hundreds of miles into Mexico and positioned some troops on the new 'border' and waited for Mexican patrols to notice. Four US troops were riding on a patrol when Mexican soldiers saw them and attacked - and bang, we were defending ourselves from Mexican aggression.
'Remember the Alamo', where rebels moved into Mexican territory and created an insurrection against the Mexican government who cracked down on them years earlier didn't hurt.
'Remember Custer' was a rallying cry justifying our slaughter of Native Americans after they defended themselves from an attack force led by George Custer.
We went to war with Spain and took Cuba triggered by a mysterious explosion of our battleship in Cuba, which could have been Spanish sabotage, or false flag, or accident, but in this case, remember the famous claim of a major newspaper publisher that given pictures of the situation, he'd get the nation to go to war:
Frederic Remington, an artist hired by Hearst to provide illustrations to accompany a series of articles on the Cuban Revolution, soon became bored with seemingly peaceful Cuba and wired Hearst on January 1897:
"Everything is quiet. There is no trouble. There will be no war. I wish to return." To which Hearst's reply was: "Please remain. You furnish the pictures and I'll furnish the war."
Quoting Wikipdia there and following, cause was again manufactured:
The Spanish-American War (April–August 1898) is considered to be both a turning point in the history of propaganda and the beginning of the practice of yellow journalism.
It was the first conflict in which military action was precipitated by media involvement. The war grew out of U.S. interest in a fight for revolution between the Spanish military and citizens of their Cuban colony. American newspapers fanned the flames of interest in the war by fabricating atrocities which justified intervention in a number of Spanish colonies worldwide.
Several forces within the United States were pushing for a war with Spain. Their tactics were wide-ranging and their goal was to engage the opinion of the American people in any way possible. Men such as Isaac Temple, the owner of The New York Journal was involved in a circulation war with Joseph Pulitzer of the New York World and saw the conflict as a way to sell papers. Many newspapers ran articles of a sensationalist nature and sent correspondents to Cuba to cover the war. Correspondents had to evade Spanish Authorities; usually they were unable to get reliable news and relied heavily on informants for their stories. Many stories were derived from second or third hand accounts and were either elaborated, misrepresented or completely fabricated by journalists to enhance their dramatic effect. Theodore Roosevelt, who was the Assistant Secretary of the Navy at this time, wanted to use the conflict both to help heal the wounds still fresh from the American Civil War, and to increase the strength of the US Navy, while simultaneously establishing America as a presence on the world stage. Roosevelt put pressure on the United States Congress to come to the aid of the Cuban people. He emphasized Cuban weakness and femininity to justify America's military intervention.
One last example, not long after when Woodro Wilson reversed his policy against entering WWI and wanted to enter, he hired thousands of people to travel the US giving speeches to build public support, which was against entering the war (a great book about his experiences with this as he wrote propaganda pamphlets and grew concerned about the ability to manipulate public opinion this way in a book that ripped apart the reliability of citizens to form well-based opinions in the face of propraganda that is very relevant today, called 'Public Opinion'). This wasn't entirely successful - many people said we should not enter the war, and over a thousand, including a presidential candidate, Eugene Debs, were jailed for years as a crime for speaking out against our entering.
Every time the public comes to feel it's been duped or entered war wrongly, there's some determination not to get fooled again, which wears off.
It was simpler when there was plenty of time for Congress to meet and decide whether to declare war. Today's global presence can easily trigger events.
There are armies of specialists in how to influence public opinion, planting stories of threats and injustices to build the appetite to 'defend our honor' or whatever.
9/11 was immediately seized as an opportunity to implement two Bush policies the public wouldn't accept before - invading Iraq, and neocon presidential powers agenda.