India is ahead of Pakistan and it's economy is in better shape mostly because of American largesse. The US wants a counter-weight to China and they think India will provide them with such.
The whole containment of China strategy will collapse if either India decide to not participate or is unable to. Now India will be able to dedicate more of it's assets against China if somehow the Pakistani threat goes away. This is where the whole design of the US strategy comes in to work. That is to turn the Pakistani Army into a counter-insurgency outfit, without the backbone to go eye ball to eye ball against India.
The US still is the sole super-power and what it decides to do in Afghanistan and what role it assigns to the regional players, will have a major affect. But this is not to say that Pakistan doesn't have a choice.
At this juncture Pakistan can either listen to the American diktats, become a second rate power, and accept India as big brother or join the Chinese camp and say no to American global and Indian regional hegemony and be in-charge of it's own destiny.