I think building solidarity and values is tremendously important, and here's why: what is the government really responsible for? Even as you go down the political spectrum to libertarians (short of anarcho-libertarians), you have consensus that government should at least provide security, from domestic crime and international threats, the enforcement of contracts, etc. Most people would go on to say that it's the government's job to provide at least basic education, utilities and transportation, etc, and do so with low waste and corruption. Fostering a culture of solidarity and shared values goes directly to those basic functions of government.
When you look at Scandinavian countries, and wonder how their systems work so well, you have to consider how shared culture and values plays a role in that success. When you wonder why the welfare state works so poorly in the U.S., you can't ignore the impact of the tremendously acrimonious culture we have, steeped in animosity between the races and between different socioeconomic classes. And if you go further down the spectrum of dysfunction, you can't help but notice the stark contrast between the extensive but relatively corruption-free governments of the Scandinavian countries and the very limited but highly corrupt governments of places like India or Bangladesh. I think that comes from a lack of solidarity. There is no motivation to, say, not take a bribe, if your mentality is that you're only in it for yourself.