can USA collection agencies collect from someone in Canada?

Answer 1

if the company that you owed the debt to sold your debt to an american company they can. you now owe the money to the collection ageny.

Answer 2

They may or may not be able to enforce the debt in a Canadian court. That doesn't matter anyway because they don't collect though the courts 99% of the time. They pressure you the pay them to leave you alone. Harassment works just as well in ANY country.