Agent Orange was technically not a chemical weapon, it was just a common pesticide used in extremely high concentration
That is a pretty weak justification because... Lets just pretend for a second that it was completely harmless to human beings.
They are intentionally causing a famine that will essentially destroy the entire country and they had no intention of bringing supplied to offset this.
Honestly, the only problem I see here is that they've failed to win despite doing so. Might be because I'm from a particularly uncivilized country, though.
The War of Vietnam ONLY stopped because the US citizens were so sickened by the war that they forced the government to stop... It really was a war of eradication and was absolutely devastating not just to Vietnam (North AND South... Yes there was a difference) but also to a few surrounding countries due to the fallout.
There was so much wrong with the Vietnam War I don't even know where to start...
About the only wrong thing about Vietnam War was that USA has destroyed the professional core of its army via idiotic practices beforehand, and thus had to rely on what was, effectively, right-wing militias, with expected results (i.e. little military success, a lot of massacres).
Oh, and also the fact that they've lost and let the communists win. Losing wars against tyranny of failure that is communism is unacceptable, especially for a democratic powerhouse country like USA.
And the Government's response to being forced to pull out of World War 2, the "Civilized Country" that clearly must be better then all the others? Ohh right... That the fault wasn't that the US waged an unjust war, hurt countless lives, or all that... But rather that the People Lost Heart and that the US government should AT ALL COST manipulate the information people receive for now on so that they don't suffer "Vietnam Syndrome"
Which is why the US so tightly controls war coverage.
Well,
duh? It was a completely justified war against the encroaching red wave of communism, which btw was killing literally dozens of millions of people by that time with mass famines in China. The only unjustifiable thing was that USA fucked up its army because it thought that it could rely on nukes to carry the day, and then the stupid politicians demanded to carry out non-extermination operations, which precluded the use of nuclear weapons, ending up in Reds taking over and ruining yet another country.
Thankfully, at least USA has learned from that lesson, and has built up a good strong army afterwards, while successfully pulling the same Vietnam-war trick on USSR, ending its existence and ensuring a decade or two of real world-wide peace, or as close as you can get to it IRL at least, leading to our current massive rise in quality of life for the whole world.
Sadly, it seems that it has become too complacent, and has failed to end Iraq properly, as well as forgetting about Russia, which now threatens to end this era of peace for the world, and letting China to build up its military and threaten its Asian allies. Hopefully, USA won't have to go through another prolonged war to adapt and properly defeat its enemies to usher in a new era of peace once again...