Email or paper mail. I got a speeding ticket from Town of Tonawanda near Buffalo. That is what I did. US has a strange system. Traffic ticket is issued by the State. But prosecutor work for the local government. Parking tickets (or non-moving violations) also is collected by local government. So the prosecutor has a great incentive to make a deal with you, especially if you are not living in the US.
So you have to tell them you are Canadian. Sorry about speeding, not familiar with the speed limit. Can you change to non-moving violation. They will change your charge and you pay the fine. End of story.
Lot's people have done it (including me)...