In I Am Malala, Should the Pakistani government have created the truce with the taliban? Why was the US government so unhappy with it?

This is a political opinion. The Pakistani government either accepted the Taliban or would have to put up with domestic terrorism within the country. Giving the SWAT Valley to the Taliban was an appeasement. The united States was against any anti-Western militants having power in Pakistan.

@Aslan : I was told the 2nd question was because they are unhappy with it b/c they think that the Pakistan Government has givin into the Taliban.

You are correct. The Taliban were seen as anti-western militants.