It is the country that the paperwork is filed in for the adoption. Since you live in Canada, the paperwork would be filed there making it a Canadian Adoption. With that said The US would recognize the adoption should you move there.
I have an adoption question. My two moms are going to be married soon..biological mom is Canadian, second mom is American. Second mom wants to adopt me...will that count as an American adoption or a Canadian one? They live in Canada right now.