As a Canadian who once had a "green card" that enabled me to live in the US I would say for sure, 100%, this is a scam.
First, as others have said, Canadians only need a passport to visit the US. We do not even need an ESTA to visit the US like people from other countries need. In case the scanner then tries to say this is the document they meant, an ESTA is only about $20, but again, Canadians don't need one anyway.
Second, a "green card" is a permanent resident card, not for visitors. The fees to get one are in excess of $500 and they can take YEARS to get. It took me, a Canadian, 9 months to get a visa to enter the US to marry and another 2.5 years to get my "green card". It is not a quick and simple process
