Trudeau’s most radical argument is that Canada is becoming a new kind of state, defined not by its European history but by the multiplicity of its identities from all over the world. His embrace of a pan-cultural heritage makes him an avatar of his father’s vision. "There is no core identity, no mainstream in Canada," he claimed. "There are shared values — openness, respect, compassion, willingness to work hard, to be there for each other, to search for equality and justice. Those qualities are what make us the first postnational state."
This is where liberal civic nationalism leads to: to the "postnational state". In other words, a liberal civic nationalism cannot uphold a national identity at all.
Let's go through the steps to get to this end point. The Western nations were initially based on a shared ethnicity, i.e. some combination of a shared history, language, culture, race, religion and so on. There was, at least, a mainstream ethnicity from which was derived that nation's core identity - a sense of "peoplehood".
Unfortunately, the logic of liberal first principles disallowed this kind of national identity. Liberals believe that the highest good is individual autonomy, by which they mean a liberty of the individual to self-determine their own identity and values. Therefore, liberals see predetermined identities in a very negative light: they are described as chains or fetters on the individual. And, of course, the traditional national identities were predetermined - they were based on things we do not get to choose, but that are inherited. Therefore, our ethnicity had to be made "not to matter" in terms of what we might choose to do or to be as an individual. You could not "discriminate" in public policy in any way based on a person's ethny, even if it were to uphold something as important as a national identity. There was no way, in terms of liberal principle, to uphold the traditional national identities.
And so liberals chose instead to implement a "civic nationalism". This type of national identity was based on citizenship, with shared values derived from liberalism itself (equality, openness, tolerance, non-discrimination etc.).
But this was never going to be a stable form of national identity. Anyone from around the world can become a citizen under this model, which means that over time the nation will become increasingly diverse. The deep form of identity and belonging that was fostered under the traditional model will gradually decline.
What you are eventually left with is a group of diverse people inhabiting the same state, which Justin Trudeau admits is a "postnational state" without a core identity.
Goodbye nation and hello to competition for power, money, status and resources amongst a variety of groups.