It can’t happen here. That’s an avowal I have been hearing from Americans ever since my family and I, fleeing a dictatorship in our native Chile, finally came to settle in the United States in 1980.

What happened to you in Chile can’t happen here. Democracy in the US is too stable, the institutions too deeply rooted, the people too much in love with liberty.

Weary of wandering, desperate for refuge, I wanted to believe that the American experiment would not abide tyranny. And yet I remained sceptical, stubbornly wary. I had pronounced similar words about Chile, and had also once succumbed to the illusion that democracy in the land I called my own could never be destroyed, that it “couldn’t happen here”.

Chilean coup: 40 years ago I watched Pinochet crush a democratic dream Read more

Chilean democracy in the early 1970s, like that in the US, was imperfect: we had our share of civil strife, the persecution of minorities and workers, disproportionate influence of big money, restrictions of voting rights and women’s empowerment and purging of immigrants and foreigners. But the system was robust enough for the left, led by Salvador Allende, to envisage the possibility of building socialism through peaceful, electoral means rather than violence – a unique experiment in social justice that, for the three years of Allende’s government from 1970 to 1973, opened the doors to the dream of a Chile free of exploitation and injustice.

And then came the military coup of 11 September 1973 that, with the active backing of President Richard Nixon’s intelligence agencies, overthrew Chile’s constitutional government. The reign of terror that followed was to last for almost 17 years, comprising extrajudicial executions and disappearances, torture and imprisonment on a vast scale, exile and widespread hounding of dissidents. The repression that afflicted those victims was not accidental. It was a way of teaching millions of Allende’s followers that they should never again dare to question the way power was organised and wealth was distributed in the world.

Such deliberate savagery was only feasible and normalised because millions of Chileans who had felt threatened to their core by the Allende revolution accepted this war on their compatriots as necessary to save the nation from communism – even if there had been no human rights abuses by Allende’s government and absolute freedom of assembly and the press. Whipped into a frenzy by a campaign of hate-filled lies, the supporters of General Augusto Pinochet were persuaded, as in Franco’s Spain, that democracy was a cancer that had to be eradicated in the name of western civilisation.

In time, enough Chileans came to their senses and, through popular mobilisations and at great cost in lives and pain, created a coalition that restored democratic rule in 1990. But the consequences of those traumatic events, the division of the country against itself, persist today, 45 years after the military takeover. We also, however, emerged from that tragedy with insights that might be relevant to this current moment in history, when democracy is under siege in the US and across the globe, with countless citizens enthralled by strongmen who manipulate their frustrations and resentments and play to their worst nativist instincts.

Facebook Twitter Pinterest Armed guards watch for attackers as Chilean president Salvador Allende leaves a building during the military coup in which he was overthrown. Photograph: Keystone/Getty Images

There are, of course, significant differences between the situations in Chile almost half a century ago and in the US today. And yet the similarities are sobering. Having once lost democracy in Chile, I can recognise the signs of malignancy that fester in the US, a country of which I am now a citizen. I reluctantly note in my adopted homeland the same sort of polarisation that contaminated Chile before the coup; the same weakening of the bonds of a shared, inclusive national community; the same sense of victimhood among large swaths of the populace, troubled that their command over the traditional contours of their identity is slipping away; the same faulting of intruders, upstarts and aliens for that loss; the same tensions and rage exacerbated by shameful disparities in wealth and power. And, alas, the same seduction by authoritarian, simplistic solutions that promise to restore order to a complex, difficult, menacing reality.

Blaming this on a president contemptuous of the rule of law, who inflames confrontation in a country urgently needing consensus and dialogue, or the cowardice of leaders of his party who have enabled such intemperance, or a foreign power for intervening to stir havoc, misses the crucial point and does not answer the question of how to stem such a tide of rising illiberalism.

Again, Chile provides a blueprint, warning us that democracy can be subverted only if large multitudes stand by and look away while it is corroded and demolished. Our deepest values are in most danger when people feel defenceless and despairing, mere spectators watching a nightmare slowly unfold as if there was nothing they could do to stop it, ready to abrogate their responsibility. It is ultimately the passivity of those silent accomplices that eats away at the fabric and foundations of a republic, leaves it vulnerable to demagoguery and dread.

The main lesson that the Chilean cataclysm bequeaths us is to never forget that the rights we take for granted are fragile and revocable, protected only by the unceasing, vigilant, vigorous struggle of millions upon millions of ordinary citizens. Salvation can’t be outsourced to some sort of heroic figure who will ride to the rescue. The only real saviours are the people themselves.

Unless we understand this, we risk awakening one day in a land that is unrecognisable, with consequences that will be paid for by generations to come. My message to my fellow Americans, and to many others abroad, is alarmingly simple: do not cry tomorrow for what you did not have the courage and the wisdom to defend today.

• Ariel Dorfman, an emeritus professor of literature at Duke University, is the author of Death and the Maiden and Darwin’s Ghosts