This song was written for Expo 67 in Montreal, which itself was a celebration of Canada’s 100th birthday. It was written by CBC personality and jingle writer Bobby Gimby, known as The Pied Piper of Canada.
The song was written for a documentary about the Centennial, but teachers loved the patriotic message of "Ca-na-da" and led the demand to release it as a single. It remained at the top of the charts throughout 1967 and in 1971 Gimby donated the song’s manuscript and all future royalties to Scouts Canada.
It features two children’s choir - one in French and one in English. There’s two versions of the song but both are bilingual, they just flip the order. For the English audience, the first verse is in English. For the French audience, the first verse is French. The first chorus is in the same language but the second chorus is a mix of both. It’s sung as a round, something you don’t really hear anymore.
It’s Canada Day so enjoy your song of the day!
Your mention of rounds, reminds me that this is a fun one, which I hadn't thought of in a while (link includes the lyrics and a link to listen to the song): https://harmonpublishing.com/jan/music/library/echo