As things are now, the US is going to have an uphill battle maintaining an influential role in international affairs. Countries like the U.K. are reluctant to co-operate with US security agencies because of fear that detainess or those arrested would be tortured or oherwise refused any legal protection. We are the losers in this and other scerios.

it is imperative then, that the US regain trust. To so so, we must own up and face up to past errors, and we must do so publically and dramatically to make sure it's noted.

On the other hand, hasty action could well be counterproductive.
The State Dept has been in talks for several years with other countries trying to clarify the various steps and variations in detainee treatment. While other countries are united in condemning the US, they are far from united as to what the right answer is.
Before we jump in with a unilateral definition of war crimes, we need to have a much clearer idea about what constitues proper procedures from the time someone is detained and throughout his peiod of detention.
The worst thing would be to have to go back and redefine all over again.

At this point, we are not ready to proceed.
There is no reason why the subject of war crimes can not be revisited when we are ready.