If Canada joins the EU, Canadian representatives to the European Parliament would need to be elected via proportional representation, it's part of the requirements.
There is no uniform voting system for the election of [Members of the European Parliament]; rather, each member state is free to choose its own system, subject to certain restrictions:
hans island is uninhabited, and the border is technically shared with greenland. its people are eu citizens, but greenland is not in the european union. they exited the eu's predecessor organization before the eu was formed from it.
Saint-Pierre and Miquelon is a way better example. Only 19km away from Point May in Newfoundland.
French Island with ~6000 residents. Full EU member. {Edit: I might have been wrong on full EU member, seems to be kind of a member but kind of not} You can take a ferry there from Canada.
The definition of what’s European is squishy and doesn’t necessarily conform to geography. It could be qualified by shard values or borders if EU members agree.