When I contacted Canon Canada, by email and phone, they assured me both times that any Canon product bought in the US with a US warranty IS covered by warranty in Canada (hence the double us/can warranty card).
Otherwise, I would not have bought my 2 lenses from the states.
Yes, when you buy Canon products from the US, they have a double warranty card for BOTH Canon USA and Canon Canada.
Here is a picture of my warranty card for my 85mm lens purchased in the US.
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Also, if you read the back of the warranty card, it says:
The Limited Warranty set forth below is given by Canon USA Inc, in the US and Canon Canada Inc in Canada (herein referred to collectively as Canon) with respect to the Canon Binoculars and Photo Lens Products packaged with this Limited Warranty and identified by model number on this Limited Warranty Card when purchased and used in the US or Canada.EOS R6 Mark II - Sigma 50/1.4 Art - Sigma 14-24/2.8 Art - Canon EF 70-200/2.8L Mark III - Godox Xpro-C - Godox TT685C x2