The whole purpose of the Iraqi Invasion 2003 was to stop Saddam Hussain from selling Iraqi oil in Euro. In 2000, Saddam Hussain announced he will switch the petroleum currency from dollar to Euro, which the US fears will encourage all OPEC members to trade in Euro. If this ever happened, the US economy will become like Africa's economy, because the petrodollar collapsed. To give them a reason to invade Iraq, they set up 9/11 which they say was done by Al-Qaeda who apparently were stationed and trained in Iraq, and also the claims of weapons of mass destruction. Now that Saddam Hussain is dead, there is no one keeping Iraq stable, which is basically a ground war between the Iraqi Army and Isis.
It's the fault of the entire US government.