Gene Wolfe
I began with Teutonic Myth: Valhalla above, the elves below. When I needed another layer, I added one. The lowest is not Muspel.
'Hour of Trust' was inspired by a Damon Runyon story, 'A Light in France.' It's basically an early WWII story, written when most people expected that world war to be much like the first one. I read 'A Light in France' and started playing with the idea in an SF setting.
He's not rewarding us by talking to us. He's talking to us because He has something to say to us directly, as opposed to the things He says to all humanity.
Ambiguity is necessary in some of my stories, not in all. In those, it certainly contributes to the richness of the story. I doubt that thematic closure is never attainable.
A youthful American voice isn't particularly challenging - I've been a young American, and they're all around me. I can walk from my house to Barrington High School.