It is absolutely amazing what happens when a President who knows nothing more than community organizing takes over Middle East operations. When Obama took office in 2009 he immediately called for troop recall in Iraq. Two years later we left the then free Iraq nation after sacrificing many men and women to give the Iraqi's freedom and peace.
When Coalition forces were there we were making a difference day by day. The country was healing itself from Saddam Hussein, elections were being held, troops and police officers trained, and citizens for the first time in a while both men and women were being educated.
On top of all that the Kurdish people up north were making their case peacefully to separate itself from Iraq and become the recognized country of Kurdistan. Al Qaeda in Iraq (AQI) terrorist forces were being defeated and most of the Islamic State of Iraq (ISI) leaders were locked away or being tried for crimes by Iraqi courts.
Then we left and the Arab spring happened that in turn spiraled into radical muslims in Libya taking down Qaddafi that lead to Benghazi on Hillary Clinton's watch, that ultimately led to the war in Syria, and finally the merging of terrorist in Syria with ISI to become ISIS. The Islamic State was around for years before anyone heard about it. The reason you didn't hear about it was because Coalition forces had them contained. Then the Obama Administration in their infinite stupidity decided to let them out like a rabbit out of a hat.
Iraq wasn't fully trained and wasn't ready to handle these threats on their own, but that is what happens when you have a weak administration that is uneducated fully on how volatile the Middle East is. ISIS isn't the United States fault it's the Obama Administration's fault.