Well, if they actually withdrew when they said they would rather than sneaking in the night months in advanced, the Afghan government could have prepared better. If they didn't abruptly stopped supplies the Afghan air force wouldn't have been grounded and some more troops could fight. If they didn't press Kabul to release Taliban prisoners they'd have more cards to play. And someone could have done fieldwork to prevent the predictable defection avalanche (a bit of money to select warlords would have helped). And if the withdrawal process wasn't so transparently lopsided in favour of the Taliban, Afghan factions wouldn't have assessed the Taliban as the winners, which would have again helped to stop defections.

But that the withdrawal was done with maximum spite is just the latest bout of ideological incompetence, and not the real issue. The real issue is how the US is so entirely self-absorbed it can't even begin to understand another country, much less try to act in someone else's self interest. Until that is fixed there's isn't much the US army can do regarding counterinsurgency, aside from the 'do no harm' principle (and this change to the status quo in AfPak is very much 'harm'). And maybe letting smarter countries lead for once.