Getting involved with Israel, and overthrowing one regime and propping-up another, and bombing them, and then sending troops and occupying them, and rinse and repeat has made it a huge mess. If it weren't for the profit from the oil, and the influence of Saudi money and the profits from the entire process, it would never have been looked at twice.
Those people are just like us. If you leave them alone, they will fight with each other, JUST LIKE WE DO! If you give them a common enemy, they'll focus on that, JUST LIKE WE WOULD. Saying that "if we left, it would be worse for us", or any variation of that, is pure speculation. It might be, it might not be. One thing is for sure, it hasn't been tried and things only get worse the more we continue to f*ck with them. Drone-bombing can kill innocent people just as well as a mortar by a US soldier. For every innocent life taken by American hands, or any Western ally's bomber jet, you're guaranteeing a future potential terrorist by their survivors. The same thing would happen here, if the roles were reversed. Revenge can set-in no matter what color, nationality, gender or religion you happen to be.