The criteria you used for judging the number of US personnel WIA is a pretty high number... Purple Hearts are awarded (signifying a WIA, and probably the basis for the number wikipedia uses) if the skin is broken, yet I don't think that would be considered 'wounded' in the traditional sense that would employ your 1:2 ratio. So a more accurate number of wounded US personnel would be those wounded and not able to return to duty within 72 hours (13,xxx according to wikipedia) or maybe even those just medically evacuated (8,xxx). I don't think medal chasing or concern for more benefits applies to the Iraqi insurgency, so that would eliminate a good number of the US casualties in the 29,xxx figure you used. This obviously doesn't apply to everyone, but it's certainly behooves you to have an injury recorded in your record book if you ever want to get treatment, compensation, or recognition for it.

Also, I think the terrorist number of WIA/KIA might be higher if they actually went to hospitals to be treated (and thus recorded). Hospitals being an apparatus of the gov't (which you certainly don't support). According to the U.S. military, the number of insurgents killed is closer to 23,000 as of June 2008. This is probably inflated too, because body counts in general are pretty vague, especially when they involve explosions, and indiscriminate numbers of people.

Another thing - terrorists aren't rational about life and death. Most are poor, probably single, without families... while the U.S. military is rich by comparison, have families, and generally want to live. It's just a job for most of us...