As a non-native English speaker, I say that none of the spellings bother me (although I've never seen Canadian spelling, or maybe I did but never knew it was Canadian lol). The English teachers I've had are all confusing as hell. One teaches us to spell the British way (or do you say 'English way'?) and others teach us to spell the American way. Like, what the hell.
Same with pronouncing things. For example the word 'fast'. (Or words like dance, mask, past, class, can't etc) I don't know how to explain it but I guess you know how Brits pronounce 'fast' and how Americans pronounce 'fast'. I've had teachers who were totally into the British pronouncing and other teachers were totally into the American pronouncing.
So, at some point I chose which way I wanted to write 'cause I started to mix up both spellings, and I chose American. Not because I don't like the British (English?) spelling and pronouncing (in fact, I find it really pretty) but because I listen to a lot of American artists and I'm signed up on American websites, so that's why. I used to have contact with a girl from Wales and one from London and I loved their slang and typical words like 'rubbish' and stuff. I learnt a lot from those girls but not long later I got in contact with an American girl so when she said something like "it sucks" I replied with "yeah, it's rubbish" and she was like "huh, what?" then I was like "oops!" to myself.
It's too bad I lost contact with all of them. It's hard keeping contact only via the internet.
Anyway, for me it doesn't matter if I read a fanfic written by someone from the UK or someone from the USA 'cause I've been taught both ways.
Oh, something off-topic but one time in English class we had a spelling test at the same moment I chose to spell and pronounce the American way. However, I forgot my current teacher loves the UK (she visits London ten times a year... no seriously). So, she put the test in front of us where you had to translate Dutch sentences to English. Many words could've been spelled differently; British and American. But I spelled everything the American way so when she let everybody say their answer one at a time and it was my turn to tell how I spelled it, my teacher said "no, you're wrong. It's this, you spelled it the American way". So I replied with, "But ma'am, this is English class. No one ever said if this was British English or American English. How am I supposed to know?" (mind you, we had to speak English throughout the whole class unless someone really doesn't understand it or doesn't know.. and I had a lot of people in my class who didn't know anything at all) Ever since then she accepts both ways.