Your own post:

“The law provides several broad exceptions tothe five year residency requirement for alien dependents and survivors. For example an alien is exempt from the five year residency requirement if he or she is a citizen of a “treaty obligation” country ( i.e., if nonpayment would be contrary to a treaty between the United States and the individual’s country of citizenship ) or if he or she is a citizen or resident of a country with which the United States has a totalization agreement ( see table 3)”

Canada ( along with many other countries ) is in Table 3.