The Americans attacked their sworn enemy Saddam Hussein in Iraq in order to overturn the Sunni Arab minority that was ruling and was oppressing the Shia Arab majority, and the Sunni Kurds. By overturning Saddam Hussein the oil of the Shia Arabs in South Iraq would freely flow to the Persian Gulf, and the natural gas and oil of the Sunni Kurds of Northern Iraq (Iraqi Kurdistan) would freely flow to Turkey, the Mediterranean Sea and Europe.
As long as Saddam was ruling Iraq the Americans would need to impose economic sanctions against Iraq because he would use his oil revenues to buy arms and support terrorist attacks against the United States.
For more details see “The Truth About the US Invasion of Iraq in 2003”.
https://iakal.wordpress.com/2015/12/02/the-truth-about-the-us-invasion-of-iraq-in-2003/
Image 1
http://gulf2000.columbia.edu/images/maps/Iraq_Ethnic_lg.png
Image 2
Image 3 Oil (black) and natural gas (red) of the Middle East
