In case of US, Taliban was supported by a hand ful of policymakers who were in charge of foreign affairs. They don't have any problem in giving/withdrawing support as the situations demands, on the basis of US national interest percieved by them. The general public in US didn't give a damn about Pakistan one way or another they were only interested in defeating the Soviets.
On the other hand in Pakistan, Taliban have traditionally enjoyed some level of grassroots support from the general public. It is much more difficult to change general public opinion than that of policy makers. It requires sustained media campaign in the urdu/local press and other propaganda which we are doing.
As for arming lashkars , I am not so sure if its such a good idea. Of course we should definately turn people against the Taliban by the above mentioned means, but arming the local lashkars while giving short term dividends, in the long term can create problematic future scenarios. We shouldn't forget that we are having so many problems today because we pumped arms into the mujahidins during the 80's at the behest of US. Now some of those arms are being used againtst our jawans :(
Just my two cents :)
Good post. You make valid points, main problem now is local sympathy for taliban and jihadis.