RE: "… in a well functioning society such as Canadian … "
This is a description of temporal perception, not a description intertemporal outcome. As such, it is not a description of the merits of a society (which would require some sort of result to judge over time) but a description of the current state of human experience in society, despite the possible, and as yet unknown outcomes.
Canada is not so much a multi-cultural society, as an uncompetitive resource economy, with little or no productive innovation, that chose to sell off it’s resources to immigrants in order to create jobs that could not be obtained by capital concentration and intellectual competitiveness. There is vast cultural war going on between the french classes and the english, and the country does not even have a formal constitution because of it. But economically, it is simply doing what the US did in the nineteenth century: selling off land for redistributive ends, and calling it productivity. Productivity comes from increasing the amount of wealth created by the same number of people working fewer hours, and by that process, transitioning the economic status of individuals above their prior state.
The question remains as to whether the resulting civilization, over some period of time, when this economic construct is no longer possible, results in integration of the people by breeding and culture, or fragments the society into subclasses and civil unrest or civil war.
This is, before discussing the impact of debt expended in anticipation of productive increases in society that appear not to be realizable in a world wherein capitalism has been adopted, and therefore productivity is increasing, in vast civilizations heretofore hindered by their lack of institutions of calculation and incentives. (the most important of which is truth telling, and contract adherence, and non-corruption)
(For example, ontario is very close to financial collapse if the property values decline as they have in started to in western canada. This is compounded by the fact that the entire great lakes area, which was developed in order to manufacture goods for western expansion, is the only major resource area in north america that is in decline.)
The end result, which is evident already in canadian society, as well as all advanced western societies, is that the initial entrepreneurial class of immigrants integrates fairly well into the commercial order but remains culturally segmented in family and social orders. After the entrepreneurial class, he more primitive cultures are forming, as they do in europe and south america, a ring of perpetual poverty around the urban centers, and are forming a permanent dependent class that requires more financial support than is given to the aging domestic population.
Whether the political construct that is a remnant of the old english order, will persist under that diversity is open to question. Or, more likely per history, that society will re-fragment and political and cultural strife will ensue. Nationalism was the result of cultural differences seeking political status. Cultures do not integrate. Certain groups do assimilate. But cultures do not integrate.
Everyone is all happy under plenty. But under pressure, everyone reverts to his culture.
It may be worth noting that prior to the fall of the great monarchical orders in europe, most sub-populations existed in multicultural enclaves in the urban centers, and got along famously for the most part. THen democracy made nationalism possible - cultural states rather than poly-enclave states. And vast wars resulted from it.
Freedom of property and association is good for productivity. But political freedom leads to the problem of marginal indifferences that cannot be resolved between groups, because in the end, they lead to differences in social status that are intolerable by their elites. We can have multiculturalism, in that sense of enclaves if we wish to return to monarchy run by a homogenous dominant culture, and a plebeian multicultural house that redistributes productive gains from the creative and productive classes to the consumer classes. But status seeking among groups cannot function in a pure democracy without eventual civil unrest. There cannot be any hope of obtaining absolute cultural power if we wish to have enclaves. (Because we will not get integration. It does not happen.)
For this reason, parliamentary monarchy was possibly the finest form of government that we ever invented. It prevents the problem of king-of-the-hill games by minorities seeking to advance their status.