A hundred yrs ago I was working with our club to increase attendance at our annual show -- all club members know how important it is to at least break even!
One of the things we did was obtain a listing of members from the AMHA, AMHR (& now you have ASPC) for all surrounding states. We prepared a 3 page info with maps, distances, hotel, camping, judges, classes, etc and mailed to those farms. A little expense but, worth it! In your case I'd say to include things discussed here about borders, certifications, etc. ALWAYS have some phone contact numbers for those able/willing to answer additional questions. We sent these to trainers who were known to travel to shows a further distance, also. Just a thought!
Yep, seeing the listing in scheduled shows is not enough for those who are intimidated by the thought of crossing the border, travel time, etc. It's the unknown. Subtracting some of the mystery will help encourage them to come there.
While I've been to Canada for vacations, never did show there when I was actively doing that. In early to mid 90's we had lots of shows going on.
Canada was beautiful, fun and friendly!