September 11 fundamentally changed America — or so we’re told, in a flood of 20th anniversary commentaries. I’m not so sure.

Much is made of 9/11’s moment of extraordinary national unity. And how transient it proved. But that shows 9/11 did not, indeed, fundamentally change the Country. It was a blip.

I’m reminded of the insight from psychology that individuals have a personality baseline, governing things like happiness levels. A dramatic event can knock you off your baseline, for a while. But eventually that wears off and the baseline reasserts itself.

Of course no historical events are immaterial. To the contrary, everything impacts everything, and there’s the apocryphal butterfly effect; small causes reverberating into big results. September 11 was a big thing. It did cause wars, and give us TSA security theater. It’s impossible to know how different America might look today absent 9/11. Trump’s presidency might well not have happened, and that too was a very big thing.

Nothing is ever inevitable. History is not some implacable force driving toward pre-ordained ends. Instead it’s highly contingent. Everything depends on what individuals do, the choices made. Like James Comey’s in 2016. And imagine if Oswald’s aim had been off by an inch.

As for 9/11 changing the country, I think the real story is that it fed into trends already shaping an America different from its 20th Century incarnation. The moment of unity was a blip, and in the bigger picture 9/11 wound up not ameliorating but aggravating the politico-cultural divisions that had been building up, even giving us yet more things to be divided over. Like the Iraq War.

And it’s not just a matter of issues to argue about. What has taken hold is an ethos of division. The issues themselves being more symptoms than causes. That’s not to say opinions are not deeply felt; people are passionate about, say, the abortion issue. But that’s actually an instructive example, because it originated with religious right leaders casting about for some issue to fire up a flagging movement, and jumping on abortion as the perfect vehicle. The point being, if it weren’t that, it would have been something else. Having the fight mattering more than what the fight is about.

What explains this? There’s a cat’s-cradle of complex factors. Humans evolved in a world where change was slow or nonexistent. Modernity has put it into hyperdrive, discombobulating minds. Triggering a primordial impulse for tribalism as something to cling onto on the roller coaster ride that life has in some ways become. What your Tribe stands for is secondary to its being your tribe — standing against enemy tribes.

Propelled by the notion that you’re entitled to believe whatever you want — mainly, what your tribe believes. So if the tribe decides, for example, that the 2020 election was stolen, then that’s what you too believe. The whole traditional information ecosystem, that used to provide a common understanding of reality, has crumbled. Part of an even broader loss of faith in and connection to societal institutions generally, with more people feeling they’re on their own. The old information system has been largely supplanted by an internet free-for-all — an information echo-system.

Nine-eleven exacerbated this. People felt threatened now by another tribe, beyond their understanding. Confidence in institutions fell even more. The world suddenly looked darker.

The pathology afflicts the right far more than the left. The right’s messaging makes clear that what gets them boiling is not issues per se but how they provide reasons to hate the other side. Having people to hate and fear is the core of today’s Republicanism. If Democrats reciprocate it, it’s a reaction to Republicans becoming truly scary. As January 6 showed.

It also manifests in what has become a Republican culture of fundamental dishonesty and bad faith. Here again the parties differ greatly. Say what you will about policies espoused by Democrats, at least they actually believe in them as good for the country (or world). Not so with Republicans. Look at their “ballot integrity” crusade. Exploiting the big lie of a stolen election, their true aim is not, as they claim, to make voting more secure (a non-problem), but harder for their opponents. They’re just dishonest about it.

This is what you get with tribal war when one side feels existentially threatened. No holds barred. We may have reached peak tribalism with the vaccine issue. Republicans’ reasons for vaccine resistance are bogus — their “freedom” cries nonsensical — but they need no reasons other than associating vaccination with Democrats. That’s how bad it is, when tribalism even infects what ought to be a straightforward public health matter. Partisanship so crazed that people literally risk their lives. Refusing vaccines that are proven life savers, while instead taking animal de-worming pills. And they’re dying like flies.

Nine-eleven did change America. But it was not the cause of such insanity. The terrorists could never have harmed the country so much. Our biggest threat is not Russia or China. It’s Republicans.