A Canadian cover letter looks close to an American one and behaves slightly differently. The paper is US Letter — Canada did not adopt A4 — the date is usually month-first, and the register is polite without being ceremonial. What distinguishes the Canadian letter is what it has to answer: in a country where a large share of skilled hiring involves newcomers, employers read the letter for one extra fact before anything else, which is whether you can legally work here.
Human rights legislation in every province restricts what an employer may ask about age, citizenship, family status and place of origin. The practical consequence for the letter is the opposite of what many applicants assume: you do not volunteer personal details, but you do resolve the authorisation question in a single clause — 'permanent resident', 'open work permit valid to 2028', 'authorised to work in Canada without sponsorship'. That sentence removes the only reason an otherwise strong application gets set aside.
Québec is its own market. Applications there are usually made in French, the document is called a lettre de présentation, and the conventions follow the French ones: 'Madame, Monsieur,' to open, a formal closing formula, and a place-and-date line. Federal roles and roles in bilingual organisations may accept either language, but writing in the language of the advert is the safest read of intent.