And how exactly did this 'get one group to slaughter another' work out in Iraq, because at the end of the day, it was the Sunni tribes themselves that decided to turn against the terrorist groups and not because of some Shia+Kurd slaughter of the Sunni.
Out of all the critical neighbors with influence in Afghanistan (Pakistan, Iran, Russia) how many did the US actually take on board and work with? The US isolated arguably Afghanistan's most influential neighbor (Pakistan). If the US actually has even an inkling of how to win insurgencies, it would have implemented whatever allegedly 'successful' strategy it had in Iraq in Afghanistan. You can't apply the Iraqi template to Afghanistan and Afghanistan is a complete and utter US failure with respect to defeating the Taliban insurgency, with the US government, military, intelligence and analysts running around like chickens with their heads cut off trying to find someone else to blame and pretending that 'oh yeah, if only the US could have done X, the US would have defeated the Taliban'.
Feed that BS to someone else please.