I think it must be the "race" dimension that brings out the "Baghdad Bobs".

If some broke white drifter from Appalachia ate Fluffy, there'd be no denials, just rage and bloodlust and demands for the death penalty.

Yet when people from somewhere far poorer and less educated than Appalachia do it, it's un-possible, unthinkable, and "there are no Americans in Baghdad." 

 I'm not particularly interested in this case but I think the whole issue is whether it had been an immigrant or not. The Republicans decided to go with that, and it seems it was a local.

As you say though, she happens to be black, so no one is going to make an issue out of it.