Social cohesion is a key concept in modern sociology.
There are many definitions – most of which complement each other, and the gist of them is ‘glue’.

…the glue that bonds society together…

Do you actually perceive modern society as being glued? Bonded? Together?!?

As an engineer – MSc in Mechanical Engineering, Bucharest Politechnica University 1986 – I’m primarily interested in ‘consequences’. ‘Causes’ come second. A close second but still second. Because it’s ‘consequences’ we have to face/endure directly, not ’causes’.
Whenever I feel bad, really bad, I begin by stopping everything that I was doing. To have enough time to determine the proper cause for my malaise. Identifying/dealing with causes ‘on the go’ – usually by having faith in what I already know, without realizing that it was exactly that which had led me to where I am now – is not such a good option.

Very few societies (countries, nations) continue to behave coherently. Many of them – most of them, actually, used to. Until very recently.
Yet most of my ‘recent’ colleagues – B in Sociology, Bucharest University 2009, continue to discuss about ‘cohesion’.

Communities continue to be cohesive. And, as a consequence, continue to behave coherently.
Why?
The easiest answer is ‘by definition’.
That’s how you recognize a community. A group of people who act coherently because they are ‘bound together’ by ‘social cohesion’. How that happened to be? Some other time!

Societies, on the other hand, no longer are.
Nations, which used to be whole, are now ‘fractured’. Not entirely, but they certainly behave a lot less coherently than, say, 50 years ago.
OK, this is not the first time that something like this had happened….

Civil wars are nothing new.
None of them had been ‘civil’ though. Which makes ‘civil war‘ an oxymoron
Something so ‘impossible’ that we haven’t coined a proper word for it. Something so horrible that we speak about it using an ‘impossible’ name in order to properly mark its utter impropriety.

What is new is the amount of knowledge we currently have about the whole matter. About the inner workings of our collective psyche.
How we use that knowledge, what we have understood from learning it, the manner in which we allow that information to shape our actions … that’s another matter!

Whose consequences are in the making.
There are no other ‘makers’ but us.
Also, there are no other people to bear the consequences of what we’re doing now.