Illustrating the Taliban is not the only insurgent force in Afghanistan is the US Office of the Director of National Intelligence (ODNI's) 2017 map of other Islamist groups in Afghanistan, Pakistan, Middle East, Africa and ISIS in the Philippines. (See much larger on page 9 of this ODNI Report).
The US and coalition allies have been faced with a never ending war in Afghanistan since 2001 which has cost $Billions, maybe one US$Trillion. “The estimate for the cost of deploying one US soldier in Afghanistan is over US$1 million a year.”
As one response to 9/11 Afghanistan has also cost the lives of 3,405 Western troops (see right sidebar “Casualties and losses”) including 2,271 Americans, 456 British and 41 Australians.
A problem with the US negotiating with an enemy to end a war (eg. Vietnam and now Afghanistan) is responding to US public questions “why did our loved ones die fighting?” A Government response along the lines of “Peace with Honour” or this is part of the "War on Terror" wears thin.
But how do you stop an unconventional war without clear enemy combatants, with no clear territory to take and without an enemy government to surrender?
Also the Taliban are not the only enemy in Afghanistan. Other anti-Western, Islamist, or "terrorist", insurgents operate in Afghanistan including Islamic State. Will or can the US Government negotiate with Islamic State forces in Afghanistan?