What I meant was, if the writing is good, the use of language is organic and natural, with none of that jarring "WTF does that mean?" stuff in it that makes the reader wonder about the nationality of the narrator.

Of course, that may just be me. I never notice narrator nationality, particularly, unless the narrator is a different nationality (or species!) from the characters whose stories it's telling. And even then, if there were a reason for it, I might find it excusable.

Not, I hasten to add, that I read very much Potterfic.