Because Canada is a Hague convention country, a US child custody court order WILL be recognized there.
If Dad does not return/make the child available to you for your parenting time, HE WILL BE IN VIOLATION OF THE COURT ORDER. You can go to court, have him found in contempt, etc., and eventually force your child returned to you. Furthermore, should Dad pull such a stunt, when the child is returned to you, you have grounds to petition for supervised visitation only for Dad.
You are going to be seen as a drama llama if you continue to be this thick skulled.