"The companies are located in Canada."
Translation:Die Betriebe haben ihren Standort in Kanada.
Sitz is the location of the headquarter. It's a legal term that defines where taxes have to be paid. Standort can be any location of a company. Die Firma hat ihren Sitz auf den Bahamas, aber niemand arbeitet dort.... Usually, Standort is used for Betrieb, because Betrieb is actually just a business, for example a factory, while Firma or Unternehmen are terms that define ownership and and legal status of a company, so they also have to define the "Sitz". Just as an explanation.