Let's recall that the article is saying that 40 years ago the situation was different.
Ultimately there is a lack of a unified societal contract, ironic in a country so focused on its constitution. What is the purpose of government, rules and society?
A lot of the issues in the US stem from this lack of common ground. And I believe, at the root is poor education and a sense of me vs. the newly arrived. A constant struggle to keep your spoils and not wanting to share with new people who haven't contributed yet.
The US is not a coherent country and society (yet). Still confused as to its purpose.
And yes, Trump is a great symptom of this.
The UK has this personality crisis right now, the empire is gone and a lot of newcomers have shaken up society. Brexit is a similar outcome. It needs to find its core, but as a conglomerate it is hard. Common traditions should help - but when the Queen dies, it will shake them up even more.