Check out the new Pew poll about Afghanistan. Most Americans don't believe things are going well there, and support for withdrawal is rising. But a surprisingly high number still believe strongly in the basic objective:
Nonetheless, a sizable majority of the public (76%) views the possibility of the Taliban regaining control of Afghanistan as a major threat to the well-being of the United States. In fact, nearly as many regard the Taliban regaining control of Afghanistan as a major threat as say that about Iran possibly developing nuclear weapons (82%).
I think this means there is a substantial bloc of people who consider a Taliban takeover to be a "major threat," but still want withdrawal "as soon as possible." I'm not sure that's a particularly coherent position, unless it means, "Let's hurry up and beat the Taliban so we can withdraw as soon as possible!" Which I think is a fairly universal position.