After 9/11, Le Monde declared: ‘Nous sommes tous Américains.’ The love affair was short-lived: as soon as the French declined to join the war against Iraq, American pundits called them ‘cheese-eating surrender monkeys’ and French fries were renamed ‘freedom fries’. When Obama took office, relations warmed, but the tables were turned: the new administration in Washington shied from foreign adventures, while the Elysée adopted a muscular stance in Libya and Mali, and promoted a more aggressive response to Bashar al-Assad's assault on the Syrian rebellion. Neoconservatives who had vilified the surrender monkeys now looked at them with envy.

Today a new cry can be heard among intellectuals in the US: ‘Je suis Charlie.’ It is a curious slogan, all the more so since few of the Americans reciting it had ever heard of, much less read, Charlie Hebdo before the 7 January massacre. What does it mean, exactly? Seen in the best light, it means simply that we abhor violence against people exercising their democratic right to express their views. But it may also be creating what the French would call an amalgame, or confusion, between Charlie Hebdo and the open society of the West. In this sense, the slogan ‘je suis Charlie’ is less an expression of outrage and sympathy than a declaration of allegiance, with the implication that those who aren't Charlie Hebdo are on the other side, with the killers, with the Islamic enemy that threatens life in the modern, democratic West, both from outside and from within.

Already, anyone who dares to examine the causes of the massacre, the reasons the Kouachi brothers drifted into jihadist violence, is being warned that to do so is to excuse the real culprit, radical Islam: ‘an ideology that has sought to achieve power through terror for decades’, as George Packer wrote on the New Yorker blog. Packer says this is no time to talk about the problem of integration in France, or about the wars the West has waged in the Middle East for the last two decades. Radical Islam, and only radical Islam, is to blame for the atrocities. We are in what the New Yorker critic George Trow called the ‘context of no context’, where jihadi atrocities can be safely laid at the door of an evil ideology, and any talk of pre-emptive war, torture and racism amounts to apologia for atrocities.

We have been here before: the 11 September attacks led many liberal intellectuals to become laptop bombardiers, and to smear those, such as Susan Sontag, who reminded readers that American policies in the Middle East had not won us many friends. The slogan ‘je suis Charlie’ expresses a peculiar nostalgia for 11 September, for the moment before the wars in Afghanistan and Iraq, before Abu Ghraib and extraordinary rendition, before all the things that did so much to tarnish America's image and to muddy the battle lines. In saying ‘je suis Charlie’, we can feel innocent again. Thanks to the massacre in Paris, we can forget the Senate torture report, and rally in defence of the West in good conscience.

Packer's article isn't surprising, but it's also symptomatic. He reacted to 9/11 by supporting the invasion of Iraq. He later became a critic of the war, or at least of its execution. Yet he responded to the Paris massacre by resorting to the same rhetoric about Islamic ‘totalitarianism’ that he invoked after 9/11. He even hints at a civilisational war between Us and Them – or, at least, some of Them, the ‘substantial minority of believers who countenance... a degree of violence in the application of their convictions that is currently unique’. That such rhetoric helped countenance the disasters of Afghanistan and Iraq seems not to occur to him, bathed as he is in what liberal hawks like to call ‘moral clarity’. To demonstrate ‘moral clarity’ is to be on the right side, and to show the courage of a fighting faith, rather than the timorous, context-seeking analysis of those soft on what Christopher Hitchens called ‘Islamofascism’. Packer's New Yorker article is a declaration of this faith, a faith he confuses with liberalism.

In laying exclusive blame for the Paris massacres on the ‘totalitarian’ ideology of radical Islam, liberal intellectuals like Packer explicitly disavow one of liberalism's great strengths. Modern liberalism has always insisted that ideology can go only so far in explaining behaviour. Social causes matter. The Kouachi brothers were products of the West – and of the traumatic collision between Western power and an Islamic world that has been torn apart by both internal conflict and Western military intervention. They were, above all, beurs, French citizens from the banlieue: Parisians of North African descent. It’s unlikely they could have recited more than the few hadith they learned from the ex-janitor-turned-imam who presided over their indoctrination. They came from a broken family and started out as petty criminals, much like Mohamed Merah, who murdered a group of Jewish schoolchildren in Montauban and Toulouse in 2012. Their main preoccupations, before their conversion to Islamism, seem to have been football, chasing girls, listening to hip hop and smoking weed. Radical Islam gave them the sense of purpose that they couldn't otherwise find in France. It allowed them to translate their sense of powerlessness into total power, their aimlessness into heroism on the stage of history. They were no longer criminals but holy warriors. To see their crimes as an expression of Islam is like treating the crimes of the Baader-Meinhof gang as an expression of historical materialism. And to say this is in no way to diminish their responsibility, or to relinquish ‘moral clarity’.

Last night I spoke with a friend who grew up in the banlieue. Assia (not her real name) is a French woman of Algerian origin who has taught for many years in the States, a leftist and atheist who despises Islamism. She read Charlie Hebdo as a teenager, and revelled in its irreverent cartoons. She feels distraught not just by the attacks but by the target, which is part of her lieux de mémoire. A part of her will always be Charlie Hebdo. And yet she finds it preposterous – and disturbing – that even Americans are now saying ‘je suis Charlie.’ Have any of them ever read it? she asked. ‘You couldn't publish Charlie in the US – not the cartoons about the Prophet, or the images of popes getting fucked in the ass.’ Charlie Hebdo had an equal opportunity policy when it came to giving offence, but in recent years it had come to lean heavily on jokes about Muslims, who are among the most vulnerable citizens in France. Assia does not believe in censorship, but wonders: ‘Is this really the time for cartoons lampooning the Prophet, given the situation of North Africans in France?’

That’s ‘North Africans’, not ‘Muslims’. ‘When I hear that there are five million Muslims in France,’ Assia says, ‘I don't know what they're talking about. I know plenty of people in France who are like me, people of North African origin who don't pray or believe in God, who aren't Muslims in any real way. We didn't grow up going to mosque; at most we saw our father fasting at Ramadan. But we're called Muslims – which is the language of Algérie Française, when we were known as indigènes or as Muslims.’ She admits that more and more young beurs are becoming religious, but this is as much an expression of self-defence as piety, she says: French citizens of North African origin feel their backs are against the wall. That they are turning to an imported form of Islam – often of Gulf origin, often radical – is no surprise: few of them have any familiarity with the more peaceful and tolerant Islam of their North African ancestors. Nor is it surprising to find an increasing anti-Semitism among French Maghrébins in the banlieue. They look at the Jews and see not a minority who were persecuted by Europe but a privileged elite whose history of victimisation is officially honoured and taught in schools, while the crimes of colonisation in Algeria are still hardly acknowledged by the state.

Assia is typically Parisian, in her dress, accent and lifestyle. But that did not prevent her from being reminded, at every turn, of her otherness. ‘Assia, what sort of name is that?’ people would ask her since she was a child. With its strong centralising traditions, France shuns expressions of difference, notably the hijab, but continues to treat French citizens of Muslim origin as foreigners. Second and third-generation citizens are still routinely described as ‘immigrants’. The message: don't wear the hijab, you're French; but don't bother applying for this job if your name is Mohammed. ‘When my brothers were growing up,’ Assia told me, ‘they would be stopped by the police ten to fifteen times a day – on the bus, getting off the bus, on their way to school, on their way home. Girls weren't stopped; only boys. The French are more comfortable with "Fatima" than with "Mohammed".’ French women of North African origin are doing better than men – which in part explains why some of the unemployed men take to dominating their mothers and sisters, as if they were their property, their only property. Assia is one of many French Maghrébins who have found it much easier to live outside France.

To say that France has an integration problem, and that it's in urgent need of repair, isn't to let the killers – or, pace Packer, their ideology – off the hook. It is to take the full measure of the moral and political challenge at hand, rather than to indulge in self-congratulatory exercises in ‘moral clarity’. If France continues to treat French men of North African origin as if they were a threat to ‘our’ civilisation, more of them are likely to declare themselves a threat, and follow the example of the Kouachi brothers. This would be a gift both to Marine Le Pen and the jihadists, who operate from the same premise: that there is an apocalyptic war between Europe and Islam. We are far from that war, but the events of 7 January have brought us a little closer.