Some of the posts here I believe are incorrect.
NR4 code 46
ONLY CPP - Canada Pension Plan are treated combined with USA social Security income because they are taxed in the USA under the tax treaty agreement with Canada if you RESIDE in the USA as a tax resident.
NR4 code 39
Other private pensions from employers in Canada are TAXED in Canada and Should NOT be combined with USA social security because the treaty considers them differently (assuming your tax home is the USA for that year). But I cannot find how that should be coded on the USA side.
