I see two scenarios ,
1.US/ISAF airstrikes and helo raids in Miranshah .
2.The above with an air campaign against pakistani military targets (nuclear installations ,airfields etc) followed by an invasion.
I ve got to say that the latter is highly improbable.Why would the US want to invade a country that has the seventh largest army made up of highly professional personal . Then their is the Nuclear deterrence,which you guys are grossly undermining .Has the US /Nato ever invaded a country that posses hundreds of nuclear weapons.I think an invasion in pakistan sounds illogical and inconceivable,considering that the us would have to engage in the largest military conflict ,since WW2.
But airstrike/airraids in miranshah against haqqani are highly probable ,have happened before.
I think this is what pakistan can do
1.Threaten the use of force ,before the operation.
2.protest in the UN.
3.Use its diplomatic channels ,such China (ive heard the their Vice Prime Minister is on his way) ,Saudi and turkey and the middleeast or whatever is left of it anyway.Iran can also be of help,as it considers the US its enemy.
4.Exit the WOT,make peace deals with the TTP .
5.This may sound a bit absurd but there is a huge population of Pakistani diaspora living in the EU,specially the Uk where we have more than 1 million pakistanis.Maybe the can play a role there.
6.A small nuclear test along the border,sort of a warning shot.