Your first mistake is assuming that operations against Al Qaeda in Afghanistan started in 2001. The rest of your argument is rendered moot by that mistake. The US has been operating in Afghanistan since the 90's, as a response to earlier Al Qaeda attacks. The 2001 invasion was just the final commitment in a much longer campaign.
Oh I see, so in addition to being the chief sugar-daddy and arms supplier to Al Qaeda throughout 1980s, the USA then proceeded to meddle directly and covertly in Afghanistan as soon as their "allies" won and the USSR withdrew, showing itself utterly duplicitous and untrustworthy to the locals
That, of course, hinges on how you define "victory". If all we care about is maintaining majority control over the country and preventing it from being used as a staging area for further attacks against the west, then we've already won.
By that token the Nazis "won" WWII in 1942
Under any other reasonable definition we
... we haven't achieved all of the goals we've set for ourselves, but the odds of eventually meeting them are pretty much 100%.
Yes, the time-honoured way of getting your ass handed to you: "fail to declare coherent, logical and testable goals, bloviate endlessly about 'progress' and 'democracy' and whatever other abstract and nebulous feel-good concept you can come up with, declare 'victory' and skedaddle home holding your bruised posterior, having met 'your goals' 110%! - whatever those 'goals' morphed into in the end in order to be met 110%". You did not seriously think you are the first would-be conqueror to come up with this?
The opposite forces have no chance of achieving a military victory - the best that they can hope for is that we get bored and go home.
You have an interesting way of defining "boredom", apparently measured in trillions of dollars, thousands of wounded, dead and maimed on your side and many more on theirs...
And yes, all the defenders have to do is to do what they always have done
As long as we're willing to stay, we can't lose
Which is pretty much a guaranteed loss for the USA as the "will to stay" (translated to real-life measurements of mayhem and treasury) is far, far, lower than "their" will to outlast you - they are after all fighting for their homes, their "way of life" (as they see it) and their religion (and "zealot" is too kind a word to describe most of them) - and all that on top of their vastly disproportionately lower cost of warfare!
Unfortunately, it seems likely that we will decide to leave, largely due to opinions such as yours.
No, you will leave because that is the only thing you can do. The alternative is "total war" and utter bankruptcy of the US Empire. None of the previous empires left because of nay-sayers either, they left because staying further meant Imperial Collapse (and some, like the USSR, waited a tad too long). No amount of Rah-Rah cheer leading will change basic realities of Afghanistan and the logistics of foreign conquests.
I find that truly depressing. Seems like people didn't learn a damn thing from the American mistakes in the 80's.
What is truly depressing is that Americans didn't learn a damn thing from their own mistakes in the 1950s, 1960s, 1970s, 1980s, 1990s and 2000s and the mistakes of all the Empires past: that the by-necessity belligerent Imperial foreign policy doctrine never ends well in the final tally for the Empire. You seem to forget that all of your troubles with Al Qaeda are the result of your own short-sighted, arrogant meddling in the affairs of others! You yourself created most of your own enemies, by steadfastly applying double-standards to your allies-of-the-moment, backing vicious tyrants then taking them down when they upset you, backing some belligerent bullies while condemning others, etc etc etc, whenever and however suited you, all the while braying about "rule of law" (which of course does not apply to the "oh-so-special" you) and "democracy" (which you immediately disregard if the "wrong" sort of people get elected). In some future editions of English dictionaries when one looks up "hypocritical", "duplicitous" or "self-serving", it will have "American" as a synonym.
Well, its a fine demagoguery you got there, but the actual reality was that the Taliban demanded to see evidence of Bin Laden's responsibility before handing him over (remember that Bin Laden is just a "spiritual leader" - read: "pontificating bore that talks hell of a lot but hasn't actually done much directly" as opposed to other, more hands-on operatives who worked out of Pakistan, Saudi Arabia and, in the case of the 9/11 crew, Germany) and the USA flatly refused. Following which the USA invaded declaring any and all comers as "unlawful combatants" with no rights of any kind.
So to keep your analogy straight, you have a case of my friend showing up at my house saying that you are gunning for him, following which you show up with a box of explosives and demand that I hand him over or else "because he did me wrong!". And when I say "hold on for a sec, what proof exactly do you have?" you say "I don't have to explain myself to a non-human like you, far beneath my superior Manifest Destiny self! What I say goes or else! You got 10 minutes to comply!" and then set the bomb off 5 minutes later, killing my wife and maiming my kids, following which you get the biker gang down the street to help you rummage through and "govern" the wreckage. And so now you have two mortal enemies instead of one and not exactly what could be called a "moral high ground".
This is how the Afghanistan mis-adventure is seen by "the other side" and it is of little wonder that the fight will likely go on indefinitely, Taliban having quite a bit (and growing by many accounts) of local support and very able to present itself as the victims of a belligerent, arrogant, foreign, religiously-motivated, supremacist aggressor, victims who will defend their ancestral homeland, their religion and their "way of life" against that aggressor to the bitter end.
I'd say the odds of "victory" in Afghanistan for the USA are pretty much on the same level as those of all the previous Empires ... not entirely zero but any Vegas slot machine looks like a guaranteed retirement plan by comparison.