The USA is not exactly popular with a lot of the Pakistani people and the alliance we have with their government is cause for much issue over there. The Pakistani government's main concern is the Pakistani people, so they'll obviously tailor their remarks around what they think will please their citizens the most. With governments being overthrown left and right these days, it's obviously in their own best interests to act tough. If they actually meant it, they're free to tell the US to go fuck itself at any time. But, since they haven't..