ISIS exists because Taymiyyan Salafists forced out of power by the dissolution of the Iraqi army joined with their Jordanian counterparts to create a caliphate and force everyone in the Greater Syrian region to live in it, which has been the goal of Taymiyyans since at least the 14th century in spirit, if not name. Are you saying that is a reaction to European colonialism?
I can’t tell if you’re implying the Ottomans, the Hashemites, the Ba’athists, or the United States are European colonizers, or someone else? Maybe the Hashemites, since they were allied with Britain and France in WW1 against the Ottomans?
Who do you think ought to have sovereignty in Iraq? The Ba’athists? That’s who helped ISIS gain control in the first place.