"...I was going to suggest Cheer Boys, Cheer, even though it it is a fairly general British song about emigration....I'm not sure why "The Walrus" thinks it is about Canada in particular ..."

Bob,

I made the assumption on the basis of the lines:

"Theirs shall be the Prairie and the Forest
"And boundless meadows, ripe with golden grain"
and
"The Star of Empire glitters in the West"

The former would indicate Canada/USA but the latter makes me think Canada (to a Briton of the 1850s, there was only one empire that mattered).

Regards

Walrus