I’m not too secretive about the fact that I’m not from an English speaking country.
Finnish schools teach British English from a very young age. It wouldn’t be a problem otherwise, but as I’ve grown older and more experienced I notice that I have a bad tendency to mix both British and American English. I don’t consciously pay mind to it when I write, and even if the script sounds good in my head I still wonder what the readers would think?
I still write gray instead of grey, but the problems usually arise in the for of preposition usage and irregular verbs. Is it as obvious as I make it out to be, or am I stressing over nothing? Do native speakers frown upon the mismatched sentence continuation from one style to another?
Would it tick you off to read a story where both worlds collide? Would it shatter the immersion?
I personally don’t see a difference when I read other IF stories, but that’s because I hardly differentiate between the language types to begin with. Unless someone says “trousers” instead of “pants”, so there’s that.