Increased hostility and terrorism activities are being brought on in part to the support the united states is attempting to send to the middle east. We are attempting to bribe and help peoples that neither want or need our help. America is trying to be an international peace keeping force, but this region of the globe is not advanced enough to coexist peacefully. If someone doesn't want you to do something and you continue to do it, what other expectations were the bureaucrats expecting.
Through about 1950-current America's government has been in the Middle East doing a lot of terrible things like enforcing economic sanctions that led to the deaths of thousands of people as well as more direct actions such as dropping bombs on them. To top it all off a lot of the involvement was to curb Soviet interest in the area. Everyone nowadays knows that America armed and trained the Taliban.
As much as this makes people angry, the correct reaction to the 9/11 attack wasn't to go invade their countries. Invading their countries in the first place is what caused 9/11.
Us, has involved in all these Middle East related wars from a long time. Basically it is in a path to fulfil its selfish needs, that is oil. It built up conspiracies in order to chase its needs. It caused Al Qaeda in order to maintain order which did the opposite of it and now its ISIS. The aim it has is to control the oil resource dominating areas. The next reason is to stand against Russia. I sometime wonder that US is more aggressive than Russia by covering themselves with protective screen named terrorism. I would like to say that US is the main reason for intolerance in the world.
It was them who launched the 2003 invasion of Iraq (as part of their colonial legacy -- Scotland and Denmark). America wasn't perfect, but I don't think that we've ever had the intention to build empires. A lot of our invasion was to give aid to people in the Middle East. If anything the middle Easterners hate Britain and Denmark for their actions.