Again that is YOUR version of the story .Only when the imperial enemies decided to invade iraq and divide them amongst sunni and shia did the fighting intensify, also this is basic method of divide and rule,
The American just went back home after getting Saddam's forces out of Kuwait .
The shi'i pop of Iraq suffered the wrath of the Sunni Sadam state .
This time when America went back in { I am not saying the invasion was the right thing to do , but that's another debate} thay made sure they didn't let them down .
What's happened ? Al qaeda the most deadly of all sunnis moved in .
The problem with you people is that you tend to rewrite history in your favor

The Al qaeda sunni sympathizers of your sort , where do they stand today in the fight in Yemen between the houthis and the gov of cali cabdallah salah ?
What imperial infidel power is creating a divison between muslims there