It is true I am not a fan of American spelling. Although I agree it has its place. Like America, for instance. Not in submissions to Australian journals.
Even worse than American spelling from an Australian writer in a submission to an Australian journal is a submission with half Australian spelling and half American spelling. Do writers not know or just not care? Sure, a stand alone 'z' could be treated as a typo, no worries. We all know software can change the little blighters. But not when the text is riddled with them.
As an editor, I change them all. Of course. And add the odd 'u' here and there as appropriate, although that seems to be less of an issue. I have no qualms about making these changes. Because I believe that, aside from thinking an Australian publication should be in Australian writing, any publication should have its house style, and hence consistent spelling. (This excludes intentionally misspelled words, which are part of the style of a particular piece and should remain as intended by the author.)
Not everybody agrees. I know people who think spelling choices, whether American vs Australian, or something like ice cream, ice-cream or icecream, are part of the writer's style and it doesn't matter if there are different versions within one publication (so long as each piece is consistent...presumably. We won't mention how many submissions come in with inconsistent spelling, even of the protagonist's name).
But what happens when it might be feasible that American spelling is part of the style of the particular piece? For example, in a story set in America. Obviously set in America. Or, when the submission is from an American? As a writer, I would do 'the right thing' and (cringe while I) changed my words to American spelling if I was submitting to an American publication, or at least expect the editor/s to make the changes. So, does an American writer expect the same, in reverse? Does the writer of the story set in America expect it? Does the story itself lose anything?
Does it even matter?