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:
Yes, even the UK had to accept this when they were in the EU. But unfortunately it wasn't very proportional, due to the small districts. Plus no one paid attention to EU elections, so it didn't have much impact on politics (e.g. it didn't help win any arguments about changing voting systems).
I live in the UK. And I always like to say the the US took all the really shitty bits of being British and amplified them. Brits are almost exactly halfway between being American and Canadian. Generally nice and polite, also really stubborn and resistant to change for the better, often very willing to believe a con-artist and cut off their nose to spite their face.
I love living here, and probably won't move back, but fuck me....some times.... smfh