Because the right lessons are self-evident and if you can't see that then there isn't much point in bashing my head against a wall trying to explain that, no, the reason you failed in Afghanistan and Iraq and, for that matter, Vietnam, isn't because of some failed public relations campaign.
(But I'll give it a go regardless.)
It's because, regardless of intent, war is hell, and eventually everyone will know someone who has had an arm blown off as collateral damage, or they'll read about the fifth wedding ceremony this year to have been accidentally vaporized by a cluster bomb. Everyone will either have been directly affected by, or at least know someone directly affected by, the ongoing civil war instigated and perpetuated by a foreign power. I mean, can you imagine if the Chinese tried to do nation building the US? No matter how bad it were to get in the States, people would resent that and they would be right to.
And it doesn't help that the US has a well-deserved reputation, in the Middle East and elsewhere, of propping up failed states run by ruthless, brutal dictators. You have no moral high ground to claim. None.
But honestly, this is just a basic, common sense thing. Your military should engage the armed forces of other countries when those armed forces pose some existential threat to you. In no other case is it appropriate. If you don't already know this it's because you are willfully ignorant to it. So, please just fuck off.
I never implied that it was a "failed public relations campaign" that took place in Afghanistan. I also didn't imply whether or not the U.S. was making the right decision to go into Afghanistan. My point in mentioning the lack of support of the Afghan people was pretty much the same thing you were saying. I wasn't suggesting that we needed to win them over, I was simply pointing out the fact that success was always impossible unless we had the support of the overwhelming majority. We didn't have the support, because the Afghan people (rightly) didn't want to engage in civil war, because war is a horrifying experience for anyone. As far as my statement that the war in Afghanistan was "winnable", I was speaking on a technical basis, making no claims whatsoever about the morality. I was also speaking on a technical basis when talking about the Drug Cartels. Other than saying the world would be far better off without such people, I made no claims about who should be responsible for making the decision to go to war with them. I acknowledged the drawbacks to it, and as you said, they are indeed obvious.
From a technical "whether or not it's possible" standpoint, If the majority of the Afghan people wanted to get rid of the Taliban badly enough to start a civil war on their own, the hundred thousand or so members of the Taliban would have found themselves facing an army of millions instead of a hundred thousand foreign soldiers who traveled to Afghanistan and found themselves in a world they didn't understand. The same goes for the situation in Mexico. I wasn't commenting because I think that it's my country's business to act as World Police, I just find it frustrating that somewhere around 200 million people were killed in genocides worldwide during the last century by people who are quite a bit like Hussein, Bin Laden, and the leaders of the Cartel. The world largely responds to situations like this by looking the other way when offered favorable trade agreements, or by stating that we should let other cultures live however they want, when it's never the people getting slaughtered that made the choice.
As far as the United States' policy of putting violent dictators in charge of failing nations, I, like most people in the United States, disapprove. I can't do anything to change it, but I accept the fact that it makes us look like douche-bags.
One more thing. Perhaps you feel like you are bashing your head against the wall when you try to explain your ideas because your hostility overwhelms whatever point you are trying to make. A little civility never hurt anyone.
