The Untied States is reimposing a trusteeship upon Iraq through containing the "Islamic State", since the number of American forces is increasing with Obama's announcement that he's sending an additional 450 military experts, which brings the total declared number to 3,500 soldiers and experts.

The new American strategy is based on a bunch of steps that totally contrast from the decision to withdraw from Iraq in 2011, and they can be summarized as such: 

First, training and arming new Sunni militants from various clans under the pretext of  "liberating" Ramadi and Mosul, which in this case would help the Iraqi Army and substitute for the Shia militias.

Second, establishing American military bases in Iraqi territory, just like General Martin Dempsy clearly announced.

Third, multiplying this strategy to make sure that the US succeeds in making a huge split between the major Iraqi components: the Shia, Sunni, and Kurds.

The US is using its fight against "Islamic State" as a cover because this war is entering its second year without any results on the ground. On the contrary, the "state" is expanding. American military statistics show that 75% of American aircraft fighting the "Islamic State" return back to their bases without having used their rockets and bombs due to the lack of clear targets. 

Iraq has become directly submissive to the US' mandate, which is expanding to the point of dominating its water, air, and natural resources. This mandate is in the interest of "Islamic State" because it will consider its war in Iraq as a liberation and resistance against the return of American occupation, which is now happening through the fight against terrorism.