In june 2004 alone there were 700 ied attacks on the American military and the situation has worsened since then . The amount of explosive used usually consists of 3 or 4 artillery shells or a cluster of anti tank mines , creating a massive blast. Unless your in a tank whatever armoured vehicle you are in is really of little defence when a large blast occurs . The British used sophisticated armoured vehicles here ( perfected most of their armoured defence here) and a roadside mine still usually caused multiple fatalities whenever a vehicle was attacked with a large roadside bomb. For quite some time the american troops were in completely unprotected vehicles , ordianry humvees and soft sided trucks . Over the last 3 years IEds have become even more sophisticated with the use of shaped charges and explosive penetrators .
Leaving aside the multitude of attacks daily carried out with small arms ( the British have been losing as many men to small arms fire as IEDs), snipers ,grenades , mortars , surface to air missiles , RPGs and rocket artillery the casualty rates admitted to by the americans would point to an extremely inefficent insurgency if an average of 700 ied attacks alone per month for the past 4 years had only resulted in 2000 odd thousand fatalities even with the improvements in field medical services. I dont regard the US casualty figures as at all reliable , nor do I regard the Iraqi insurgents , bloated with weapons and explosives and many highly trained former special forces soldiers as at all inefficient .
In my opinion the figures are grossly off target , unlike the insurgents .