Iraq is not even Iraq any more. It is effectively fractured into three countries, or provincial regions. Kurdistan to the north, a satellite state of Iran to the east, and what is essentially part of the Islamic State comprising most of Anbar province, to the west. There is no national unity fighting FOR Iraq any longer. Lesser ethnic minorities or tribal affiliations are essentially on their own, and have no protectorate or security umbrella under which they may be shielded.
Should the US re-invade Iraq? There is no longer a Saddam Hussein that maintained at least a facade of a national regime, and most of the factions in Iraq has little or no interest in receiving direct military support from the US, proven to be a most unreliable partner, and subject to withdrawal at any moment, on a whim or on the least whiff of political incorrectness.
“Stay the course” is an attitude long since abandoned.
In many ways, there never was what we would call a “country” in describing Iraq.
The borders follow no natural demarcation. There is no language that separates Iraqis from many of their neighbors, nor is there one national unifying language, race, etc.
In reality, it’s simply lines Lord Balfour drew on a map in the 20s.
To the locals, first loyalty is to their tribe, then their family. Next loyalty level of loyalty is to their village Next is to their sect. Then comes Islam.
Last is the concept of “country.” Literally the only thing less important than “country” is the concept of “truth!”