US interests internationally are effected though. But that still doesn't explain why its ok for a super power to negotiate but not ok for Pakistan.
I am all for blowing up Ts where you can find them, but an even effective weapon is breaking organization into two or more then turning them against each other. They both die fighting each other. Heard of the phrase 1 arrow 2 hits?
I'll tell you why - because the US has a choice to continue the war or not, Pak does not. US can simply leave Afghanistan to its fate without any negotiations or fighting, and American citizens will only be glad. Whatever the outcome, American citizens and American soil will be safe, free and prosperous. Under such conditions, should they keep spending blood and treasure to protect Afghans, or do some negotiations to bring down the fighting there, while ensuring that the state they set up there cannot fall?
If a terror attack happens on US soil on US citizens, or if their country is in danger of being destabilized by barbaric hordes, you can bet that they won't be negotiating - they will be unleashing the forces of hell on their enemies. That is a fundamental duty of a nation state. That is what they did after 9/11 - they did not bring the perpetrators to Washington, DC for coffee and cookie meetings, but chased them to their holes and caves, threw them out of power in their country, decimated their networks, and ensured that they would never be able to touch American soil or harm an American life.
On the other hand, the talibs are fighting against Pakistan in Pakistan, and Pakistanis are dying every day. A state that invites insurgents to talks under such conditions casts serious doubts on its own soveriegnity and legitimacy.