First off, regarding the US engagement policy, the United States not only meets the international requirements of the LOAC, it also exceeds them with their own ROE published as the SROE.
Here is some information on the LOAC:
http://usmilitary.about.com/cs/wars/a/loac.htm
Remember, the rules followed by the US - the SROE - meet or exceed minimum requirements of the LOAC in all areas. A copy of the unclassified portions of the SROE can be found here:
http://www.fas.org/man/dod-101/dod/docs/cjcs_sroe.pdf
The United States military, after Vietnam, found it necessary to make identification of hostiles and hostile targets as streamlined and efficient as possible. I doubt you understand the weight of this since you're probably still in high school and never had an 8-year old start tossing grenades at you. I'm not saying I have, but I'm sure you catch my drift.
Again, research on this kind of thing is important. It is irresponsible to make a broad assumption that the US engagement policy is the cause of the majority of the civilian casualties in Iraq. As I recall, insurgents managed to exceed US-related civilian casualties for a full quarter of a year in a single day. Keep things in proportion.