They don't actually care about "winning" in Afghanistan. American troops are going to be stationed there indefinitely. The Taliban still existing and also being awful reactionaries is just a convenient justification for keeping them there.

The only way they'd actually consider admitting defeat and withdrawing is if American casualties start hitting Vietnam-esque highs and a renewed large-scale anti-war movement fractured American society through civil unrest again. Until that happens Afghanistan serves as a convenient base to project covert operations into Central Asia and theyre perfectly content in ceding control of the rural regions to the Taliban