In Canada the governing body is CaLDRA (Canadian Long Distance Riding 
Association), head of both endurance and competitive trail riding.  There 
is no national endurance championship, so our biggest endurance ride is 
the North American Championships held every 2 years, which is in 
Canada at alternate times.  Competitive Trail does have national 
championships (probably because there is no N.A. champ ride), held 
every 2 years, alternating between eastern and western Canada.
I think the reason there is no national endurance championship is 
because the country is so huge, and there are relatively few endurance 
riders here compared to the US.  We are split into Canada East and West 
teams for the NA champs.
Hope this helps. Brenda
Edmonton AB