Iraq was created by the Brits after the fall of the Ottoman Empire, who sided with Germany in WW1.
Iran was Persia so yes they have been around a long time.
There was a democratically elected leader who was against foreign exploitation of ME oil resources (another thing that chafes people there. Churchill came to ask the US to protect British Petroleum in Iran and Kermit Roosevelt, a relative of Teddy, and a CIA agent came up with Operation Ajax which resulted in a coup against the elected government and the installation of our puppet the Shah. The Islamic fundamentalist forces came to power in opposition to the Shah, eventually deposing him and leading to what we have today. When you put people in charge who sell you their nations resources with benefit to the citizens, unseat elected officials, and on and on you create a lasting resentment at the least and a Bin Laden as an unfortunate worst case (or at least let's hope he's as bad as it gets).
You just can't keep screwing over a people for the better part of a century because you want to control them and take their resources even if it ruins those people and say "they hate us for their freedom". They certainly do not. They resent us for taking their wealth and choices.
Now? They wouldn't trust us whatsoever. Why should they?
Now Obama becomes another in a long line of powerful foreigners who comes to the region to kill without knowing either the people involved or the facts of the matter. They die and Obama saves face? What impression is that going to make in Syria and beyond?
That's why you don't go shooting off your "red line" mouth. You do what you must, but do it quietly and when you are very sure of the nature of any conflict and the likely consequences.
Isn't happening.