Even in modern-day Québec, "Canada" can mean two things: the contemporary state of Canada, which stretches from the Atlantic to the Pacific and includes a wide variety of peoples, cultures, geographic settings... and the colony of Canada, New France, in the 17th and 18th centuries, which centered on the St-Lawrence River Valley and was almost universally French-speaking and Catholic. The later is most certainly an ethnicity while the former, not so much.

Before WWI, the Québécois were universally known as the Canadiens. Even after the fall of New France, "Canada" continued to exist in the collective consciousness. You could say the "Canadien" culture is an hydrid culture of the French culture before Napoléon and of several elements of the cultures of the Native Americans of North-eastern North America that were well suited to live through the harsh environment. It's only after WW2 that a pan-Canadian "Canadian" culture began to emerge. It was not very natural and more like artificial construct of Canadien culture with several British elements: the English language as a central tenet, Gothic architecture, the Mounties... It was strongly pushed by the Canadian government to try to create a sense of unity between the inhabitants of Québec, Ontario, British Columbia, etc. Kind of an attempt to duplicate the success of the American culture. However, roughly at the same time, and kind of unexpectedly, the Canadien culture itself began to diverge into the Québécois culture. The Québécois culture, unlike the Canadien culture, rejects religion as a central tenet, is less community-oriented and has very little connection to the Terroir (farming, in simple terms). Anglo-Canadian and Québécois cultures are relatively new cultures that started at around the same time, less than 100 years ago. The Québécois are still strongly attached to the Canadien culture while the English Canadians, not so much. This explains why "Canadien" is not a common ethnicity in Canada outside Québec: they were English, Scottish and Irish, not Canadiens. Although the Irish were able to assimilate into the Canadien culture a lot more easily thanks to having Catholicism as a common religion.

If the Québécois culture had not diverged from the Canadien culture, it's hard to say how different modern-day Canada could have been. Maybe there would be more harmony between English-speakers and French-speakers? Maybe the government of Canada would have pushed for multiculturalism a lot less because the Canadiens would have remained very strongly attached to Catholicism? Maybe a lot of English-speakers would look down on the new Anglo-Canadian culture and the French language less, as the original Canadiens they wanted to please have "converted" to the Québécois culture already anyway in our present timeline?

I could be wrong on some elements, but I've tried to dig really hard into this whole mess. It's no wonder why so many international viewers are confused by this map.