Presumably it has its roots in France if it came via French Canadians. The French boudin blanc is also usually made from pork with breadcrumbs and cream added to bind rather than rice and is most definitely a sausage, eaten hot as part of a main course. Some of the Cajun Boudin images I've seen look very similar to the French in that the sausage is pale. But there does seem to be a wide variety of textures & colours. The one in your video looks much richer and 'reddish brown'.
Yes, it obviously has roots in France, but the amazing thing about American foods with European roots is that they are adapted to what was readily available to poor immigrants when they got here.
I never saw a lot of blood boudin (boudin noir) in cajun country when I lived there, but it is basically boudin with blood added. Don't know why... it probably doesn't mass produce easily.
But, Southwest Louisiana and Southeast Texas -- cajun country -- is the only place you might find more boudin than hot dogs or donuts.
CD