This is a very interesting read. You will get a feel of how grand schemes like AID work at high level. You will see that they are all ideal and work perfect at that level. They fail only at levels of distribution. Also see how massive the refugee problem was and how it was handled and helped by all nations of the world. Without saying it also has history of 1971. Even reference to a US spies in Russian presidents office and Indian prime minister's office(not named though).
Most notably you will see that if USA had gave one single word of advise to Yahya before the operation, Pakistan would not have suffered the loss of Bangladesh. You will see Nixon tolerated Yahya so much that he did not even give a piece of advice even unofficially about what he should have done. Also it includes Indian fears of an independent Bangladesh, Indian and chinese calculations as events progressed. Even Zulfiqar Ali Bhutto's selfishness(I don't blame him. After all he is a politician and he acted like one, that was a natural move. ) in not announcing surrender to the UN(he was at UN then). Yahya's overconfidence and the worst handling of situation by army especially during the lull between March and November, Yahya's pinch of honour when he announced surrender himself, though too late.
I recommend this to everyone interested in foreign relations, diplomacy and aid programmes and history.
Moral: US will know everything going on everywhere. They also know what will happen.
Then why could they not help Pakistan?
Ans: Decisions. They would not advise Yahya because that would be violating Pakistan's sovereignty.
Contrast this to how US is acting today with Pakistan. They put pressure on Pakistan(Yahya had a free run with everything), use drones. I feel this only helps Pakistan assuming the administration's attitude and mindset is similar now.