Context: I am a Canadian citizen who twelve years ago, I moved to the USA and married a US citizen. I have just started to receive a spousal pension under Social Security. I am also now eligible to apply for my Canadian pension, having paid into the Canada Pension Plan my whole whole working life.
Question: If I start to collect my Canadian pension, will US Social Security deduct the amount of my earned Canadian pension payment from my spousal Social Security payment?
No. Foreign pensions are excluded from counting as government pensions for purposes of the Government Pension Offset (GPO) provision, so your Canadian pension would have no effect on the spousal benefit you receive from the U.S. Social Security system (https://secure.ssa.gov/apps10/poms.nsf/lnx/0202608400).