While we're at it, why don't we imagine the sun was green, Superman wore pink and orange, and it rained Hershey Bar's every afternoon too? It would be the same thing.
Neither scenario EVER happened, and are ridiculous to imagine. Even for a "moment"....
There isn't any point imagining those things you just mentioned while mine did.
The point is that its a ridiculous notion that the actor who will ultimately be chosen to play the character should be American.
However I think my previous post makes this clear so I shouldn't have to explain this to you if you would just be willing for a moment to use your imagination especially since any discussion of a future Superman movie requires it.