1) I did not depict Montreal as a monoculture, but as  bi-cultural. The native reserves were and are still small and marginal. The fact there are pockets of marginal sub-cultures here and there does not mean a country is "multicultural" except for purists. It is, for all intents and purposes, largely monocultural.

The whole point of official multiculturalism is to help promote otherwise marginal cultures and prevent their assimilation into the majority culture.

2) Almost all Canadians shared a common familiarity with what one can characterize as broadly European, Judeo-Christian culture, historically based largely on the Bible. Almost everyone grew up familiar with art, music, literature based on it. Everyone knew the stories about Adam and Eve, Noah and the Ark, the Beatitudes, etc. on which those were based. That is a common culture.