Achieving limited objectives is something (with its own set of consequences) in war plans but taking over a country size of Pakistan is another. It is not possible for US with her might to go after Pakistan on ground.For Americans our army size and nukes mean nothing. they dont need to fight entire force.
they blind you silence you cripple your C&C and kill few thousands and send few hundred to take over.
there is simply nothing stopping them.
they are warriors and conquerors by design. their weapons are unmatched. F16s the design of the 70s. but are still among the best jets.
There is significant risk even with limited objective interference also. US don't know location of each and every warhead, what they will miss will be dropped on US bases and allies.
Just one nuclear warhead dropped on a US base will ruin the majority party's prospects for a decade or more, it is just a non starter, only thing keeping Iran and North Korea safe is the possibility of actual operational WMD's.