Are taxable only in the United States.
According to the U.S. - Canada income tax treaty, taxation of these benefits is based exclusively on residence.
U.S. citizens or green card holders who reside in Canada are not subject to U.S. tax on this income.
These Canadian benefits are treated as U.S. social security benefits for U.S. tax purposes.
Any benefit under the social security legislation of Canada that would not be subject to Canadian tax if paid to a resident of Canada is not subject to U.S. tax.
Canadian benefits that are treated as U.S. social security benefits are reported on Form 1040
(PDF), U.S. Individual Income Tax Return or Form 1040A