We get the cooperation of the locals when they figure we are there to stay, we are stronger, and it is the terrorists who are under death sentence, not them if they help or even work for or with the Americans or the Iraqi government.
your point is well taken.
Back in the middle ages, and even in the 20th century, conquerors were not worried about nation building. Conquerors had one goal, to win and then plunder. I guess there is a price to pay for fighting a kinder, gentler kind of war.