SIN, I have a six-year-old and I would never want to burden his innocence with such rubbish.
Here's a version perhaps more suitable for a 12-year old.
Neither side reasonably has the expectation of completely defeating the other. Rather, each wants their political capital increased to the extent that they have considerable leverage in whatever reality exists in Iraq long-term. Thus, "winning" and "losing" will always be relative, in the same vein as "glass half empty" versus "glass half full."
The best scenario is that the U.S. completely leaves Iraq (victory for insurgents) and, at the same time, a coalition of powers presides over a relatively peaceful Iraqi populace (victory for the U.S.). In any case, victory is in the eye of the beholder.