>>But I think there used to be geographic boundaries for parishes:<<
I don’t think that was ever the rules, BECAUSE of what you are stating.
Otherwise we would have been at the Irish parish instead of the Polish parish.
Now you’ve got me interested. I’m betting that it’s one of those rules which exceptions and general contempt have so weakened through desuetude that no one thinks about it (except me) anymore. My one copy of the canons is out of date, darn it, or I’d go check it out.