I wouldn't quite say most of the deaths have been caused by Islamic and Iraqi extremist. You have to put it into a context:
At a minimum (and most estimates are twice this) 60K killed during the first gulf war. 500K (and many are higher and with good reason) killed through a combination of sanctions, and battlefield contamination issues *(DU, CW, We did blow up the electric, water pumps, sanitation system ..and then prevent them getting the parts to rebuild it, so water born disease claimed about 20% of that total. War crime BTW.) Second war: Low ballpark is 120K killed, high is over 200K.
Even at the low end of the range, our government has a hand in the death of over 680,000 Iraqis, high end estimates put this at a near a million & growing. By most accounts, we are more deadly to the Iraqi people than Saddam and the Iran/Iraq war combined. Due to the nature of some of the munitions used, there will be regional problems for an extended period of time.
For those who doubt the effects of those munitions, I point you to the birth defect rate of more than 3 times the national average in the children of those who served in the first gulf war, and a mortality rate that is several times the average for peope (both serving and not) the national average of those people, and their extremely high disability rates. Not that the government takes care of them either. By the end of this war, we will have somewhere around 2 million people who have been rotated in and out of the combat zone, so even our own losses and suffering for this war are going to be large in the aftermath.
On top of that, we became a lot less free for it, and that is a very high cost indeed.
I roughly understand the strategic reasons they are doing what they are doing, but I am questioning whether it is worth all of that. At best we gain control, but not a monopoly, on a large chunk of the remaining old in the world, use it as a wedge to control europe, maintain our dominance in N. & S. America, and leave ourself a nice excuse to keep troops stationed in the ME and Korean penn. The cost is just ...however many of them we have to kill to do it, however many of us get hurt doing it, ruinous debt, endless suicide bombings (primarily in occupied territories), and a complete police state at home.