Human beings are change averse. We get a job, it's not the best job in the world, but it's interesting enough, so we settle down and stop looking. We find a decent hairdresser (well, OK, I don't, but other people do) and we know that there's probably a better one out there somewhere, but ours is friendly and reasonably competent, so we stick with him.

Exactly the same tendency applies to our political preferences, which is why Obamacare is proving tougher than expected to dismantle. The case against the current healthcare model is so familiar that it hardly needs to be rehearsed anymore. Obamacare pushes up both taxes and premiums; it deters small businesses from taking on full-time staff; it adds layers of complexity to an already byzantine healthcare system. These drawbacks have gone from being theoretical to being immediate to most Americans, and were a large part of why Republican candidates did so well at all levels six months ago.

So why isn't scrapping Obamacare straightforward? The GOP made repeal a big part of its program, and was elected on that basis. The party has majorities in both chambers. The president is committed to abolition. What's the problem?

The problem, frankly, is that inertia bias applies as much to politics as to everything else. Although Americans don't much like the current system, they fret that the alternatives may be worse. Regular polls for NBC/WSJ have probed public opinion on Obamacare since 2009. Those who thought Obamacare "a bad idea" consistently outnumbered those who thought it "a good idea" — until January of this year. Fox News' tracker poll showed the same thing — a sudden flip after Donald Trump's election. Not even the strongest advocates of Obamacare will claim that this reversal was because the system has miraculously started performing better. What we're seeing, rather, is what Milton Friedman called "the tyranny of the status quo." People dislike an existing policy until the moment that something else is proposed; then, grumblingly, they start hankering after the devil they know.

Human beings tend to prefer the current policy even when they have no idea what it is. A team of Israeli psychologists, for example, asked a sample of people whether it should be legal to feed stray cats. Half the respondents were told that feeding alley-cats was currently permitted, the other half that it was banned. Sure enough, both groups supported whatever they had been told the existing practice was, and volunteered all sorts of plausible arguments in favor of the supposed status quo, believing that they had reached their view wholly independently.

Congressmen know all about incumbency advantage. They, of all people, understand that it can be literally stronger than life: In 2006, the recently deceased Bob Kasun, whose name was still on the ballot paper in Arizona, won by a margin of three-to-one. And they are sensitive to the way public opinion is shifting, which is why, as W. James Antle III argued last week, it is difficult to secure a Senate majority for a properly free-market alternative.

But here's the thing: Obamacare's incumbency advantage will only strengthen with time. I argued when it was brought in that it would have to be repealed at once or not at all. Consider the British healthcare system, designed during World War II at a time of rationing, conscription and full state control. It is hard to imagine that anyone, these days, would come up with a system where the state has a 100 percent monopoly on provision. And yet, every attempt to make the system more responsive is howled down as an attack on the doctors and nurses who work in it. That's how the tyranny of the status quo works.

I have no doubt that our healthcare system, like yours, could be reformed in a way that would create many more winners than losers — among the clinicians as well as among the users. But few will see that until it happens. Indeed, even after it happens, a political problem remains: The losers will blame the government that made the change, and vote accordingly, whereas the winners will attribute their good fortune to themselves.

And so, 70 years on, we Brits retain a healthcare system that is showing its age in every sense. We grumble about it, but we oppose any fundamental change.

America is just starting down that road. It has one chance to turn back. That chance is now.