Their MRAP mine-resistant vehicles, which cost $1 million each, were specially developed to combat the terrible effects of roadside bombs, the single biggest killer of Americans in Iraq. But Iraq is a country of highways and paved roads, and the heavily armored vehicles are cumbersome on Afghanistan's unpaved roads and rough terrain where roadside bombs are much less of a threat.
Based off who's statistics? Seems to me that is just as much a threat, buddy of mine was the only survior in the vehicle and he landed 50 feet away with the turret.....

They are just as much a threat in Afghanistan.....
Iraq/Afghanistan IED comparison