Which city in Cuba is closest to Canada?

Havana.

The distance between the two places is about 4263.5 kilometers.

Havana (LaHabana) is the capital and largest city of the Republic of Cuba. National economic and cultural center. Located on the banks of the Almendares River in Havana Bay in the northwest of Cuba, guarding the door from the Gulf of Mexico to the Atlantic Ocean, it has an important strategic position. Havana is located on the northwest coast of Cuba and is surrounded by the Province of Havana. It is the capital, main city and commercial center of Cuba.