I mostly regret you people voting in obie and losing what was clearly a won war that was making progress to a stable region but you fucked it up.
Obama didn't lose Iraq. Bush did. Bush lost it because he didn't give the Iraqi people the jobs rebuilding their own country. He excluded the Iraqis at every turn.
The the Iraqis were better off under Saddam. They had jobs, food and safety. Under Bush they had no jobs, no food, no money, no infrastructure, and their country was in a shambles. The longer the Americans stayed, the more they were hated.
Saddam Hussein was a Sunni Muslim. His administration persecuted Shiites. The New leadership installed by Bush was Shias who deliberately excluded Sunnis from the new government which caused trouble between the two factions. They persecuted the Sunnis.
There are so many ways that Bush fucked up the whole occupation of Iraq that you can write a handbook on how to alienate a conquered people based on his policies there.
Taking out Saddam Hussein was a huge mistake. As bad as he was, he did maintain stability in the region. When you remove a strongman, it creates a power vacuum in an area where tribalism has been a way of life since before the birth of Christ.
Someone will always try to fill a power vacuum. ISIS is that someone.