First of all, Afghanistan is too big to become a province. Its twice the size of Baluchistan. Secondly, even if lets say Taliban take over the entire country, which btw they have never been able to. Why would they join us. They are not our vassals, infact what would happen is that they would lay claim on FATA. Since according to them, Fata is part of their Emirate. They dont even accept the Durand line. This isnt the Game of thrones dude, diplomacy doesnt work like that in real life. Their is no modern example of a country totally annexing another. This is a childish thread.