Canadian troops would remain for home defence

Why would Canadian troops remain out of the Western Front?

Britain and Canada would retain them for home defence once an American invasion became likely.

Advance warning of an American invasion would change the destination of Canadian formations. Britain would have little reason to move those troops to France when Canada itself faced attack. The Canadian government would also resist sending away the forces needed for home defence. Some territory in France might receive fewer reinforcements as Britain prioritized keeping Canada intact.