Nothing happens. Nothing. The reason those people are pissed is because of the U.S. government constantly fucking with them and poking them. Over throwing governments, secret renditions, locking up loved ones in Guantanamo with no trial indefinitely. I'd be fucking pissed too.
Obviously not much happens in the short term if we don't interfere in the affairs of Pakistan and neighbours. In the long term they might rebuild their terrorist training camps, but .. meh so what. Only a few people have been killed by terrorists, it's not a big deal and not a fundamental threat to civilisation.
You couldn't say that there would be no consequences for not engaging in the 1930s. Many more countries could have been overrun by fascism for decades.