The American military just has a worse record for it I'm afraid
I agree that friendly fire happens during conflicts - didn't the British shoot down one of their own planes during the 1st Iraq war?
I'd like to quote a light-hearted saying from WWII (and, no, I don't remember it !): "When the Germans bomb, the British duck; when the British bomb the Germans duck; but when the Americans bomb everybody
However, the recent killing of Linda Norgrove by the very people who were trying to save her, was extremely unfortunate from the US's point of view and does little to dispel the widely-held notion here that the Americans are somewhat trigger-happy. You don't go chucking grenades into places where hostages are being held.