Gents,
This is not true. This is the bastardized "American" definition of Geneva convention in that in their interpretation it does not apply to non-state "enemy combatants". However the GC applies to humanity in general whether they are state or non-state actors.
However, that aside, I don't see anything wrong with the picture. The photo was taken at the location of the incident, none of the officers or men is posing with the dead bodies gleefully. They are just standing around post action.
So in brief, USA is the most war crime committed country but in the whole world not an institution or country have courage to raise the issue.
The only victim of this clause are 3rd world countries, by their own citizen or by USA/West.