I. On Morality
Nietzsche said “every people speaks its own language of good and evil, which its neighbour does not understand”.
A people constructs its ambient morality which not only does its neighbour not understand, its neighbour may be violently hostile to. For example, in Scotland people celebrate gay marriage, whereas in Saudi Arabia gays are persecuted, sometimes even tortured and killed.
But Scotland and Saudi Arabia are alike in one way: in both countries, the majority of the population agrees that their morality is the right, just, natural morality and the normal way for humans to live. They also reject moral relativism: most would disagree that their morality is merely a semi-arbitrary point in morality-space which got their through a set of historical accidents. And in both countries, most people would regard the other country’s morality as abhorent, disgusting, decadent, and deranged: a society that thinks like that will both collapse from its internal contradictions, and moreover deserves to.
But what’s important for social cohesion is not so much what the ambient morality is, but that everyone agrees with it. If everyone celebrates gay marriage, that’s cohesive; if everyone hates gays, that’s also cohesive. One could argue (and if I took my moral relativist hat off I would agree) that one society leads to happier people than the other, but both societies would work.
Ambient moralities are only likely to harm social cohesion if they do things like praise laziness and condemn work; or praise treachery against the group while condemning loyalty; but such ambient moralities are rare as they tend to destroy the societies that are their hosts.
II. The USA
It sometimes seems that the USA isn’t one society, but two: the red states/people who praise Trump and the blue states/people who loathe him. But that’s misleading, because the people who shout loudest are the ones with the strongest emotions, so naturally everyone who is shouting is an extreme supporter of Trump or an extreme opponent. I suspect is it more likely that 1/4 of the people love him, 1/4 hate him and the other half are meh.
But the level of self-segregation of the USA into two separate communities, who increasingly don’t like or even understand each other, does seem to be increasing.
III. The West
If this trend continues, the USA will become increasingly incohesive and possibly ungovernable. This is important because the USA is the richest Western country, with the biggest armed forces, and therefore the de facto leader of the West.
It has been proposed that the 3 west coast states, all of which voted for Hillary Clinton, join Canada:
Of course, this isn’t going to happen in the short term, but in the long term if the polarisation increases, something like it could happen, possibly also with some states in the north-east also joining Canada. There could also be a one-year transition period, where leftists could move to one of the leaving states and rightists could more to one of the remaining states.
This would probably make people in both the remaining USA and the leaving states happier, because they would be in a society where a higher proportion of the people shared their values.
If it made the USA more cohesive, and Canada bigger (and thus more able to throw its weight around) it might help the West stave off challenges from e.g. China.