It used to take two hours to drive from Tikrit to Baghdad.

Since the extremists of the Islamic State in Iraq and the Levant (Isis) rumbled from Mosul to Tikrit and south toward the outskirts of the capital, however, entire neighborhoods in between have fled and most offices have closed, families have been torn apart and lives have been upended.

It takes five days, two border crossings and a plane ride to get to Baghdad now, but residents there tell me that, existential crisis aside, Baghdad is back to normal at the moment: restaurants are full until late in the evening again, and traffic has returned to its typically sluggish pace.

The Tikritis and the ordinary Iraqis on the margins, though – they have nowhere to escape the violence, and little cause for hope.

Foreign-policy analysts in Washington and the West don't realize how serious the situation in Iraq has become. Two weeks of diplomatic debates and military arguments have centered on whether the sweep of Isis through the country will lead to the dismemberment of Iraq. But when I talk to Iraqis on the ground – and I talk to them all day, every day, from emptied-out Baquba to bombed-out Tikrit – they tell me Iraq is already dismembered.

So how do we put it back together again?

The United States' decision to deploy a limited number of military "assessors" and "advisers" – to figure things out in Baghdad, essentially, before doing anything – will do close to nothing to resolve the country's immediate security threats. With such a small number of boots on the ground, the only realistic objective to which the US can hope to contribute is too simple: helping to protect the capital from an Isis onslaught.

Even if it wanted to, the US is clearly incapable of resolving Iraq's larger problems. After all, it was under the watchful eye of 200,000 American soldiers that the Iraqi military, with all its pathologies, got established in the first place. And the calamities in Mosul and Tikrit only accentuated what many have been warning of for years: Iraq's armed forces are bloated, poorly trained and equipped, and led by a corrupt and incompetent officer corps and political elite.

Although the Iraqi army still has some units that are effective and cohesive, it is spread too thinly across several provinces to attempt to retake significant territory from Isis. And Isis can always spread to other parts of the country itself – parts that are beyond the government's gaze. One of my colleagues from Baquba, 35 miles north of Baghdad, watched as Isis attacked areas in the province that melted away. "They are like a cancer," he told me. "The threat of further massacres is ever present, as is the possibility of more territory falling to Isis – including parts of Baghdad."

As someone who has studied the individual responsibility of US occupation officials and Iraqi politicians for the past decade, I watch closely how their decisions affect community relations on the ground. Sectarianism is often offered as an explanation for all the violence in Iraq, and while there's no question that significant divisions and tensions have long existed, that explanation always seems to absolve those who are truly responsible for Iraq's breakdown from any blame.

Right now, the only forces on the ground that could possibly contribute to a true resolution – to a slow putting-back-together of a broken land – are tribal fighters, particularly in the areas around Mosul. Tribal forces have an interest in regaining control over their areas from Isis, and large numbers of armed and dedicated fighters who are capable of joining the fight. It will be tremendously difficult to convince them to fight alongside government forces – in the so-called "awakening" of 2007 and 2008, they were betrayed by the central government. But it's less than a long-shot, and whoever succeeds Nouri al-Maliki as prime minister (whether it's Adel Abdel Mehdi or someone else) will have to look forward anyway.

Today, Maliki's military claims to be killing dozens of terrorists a day, but I have regularly been told about many civilian casualties, including an entire family that was killed in Baiji, the site of Iraq's largest oil refinery. That ineffectiveness – and the inherent tolerance for human rights abuses – is now systemic in the Iraq security force. Indeed, it was developed by the US throughout the Bush administration’s occupation. And a few dozen of Barack Obama's Pentagon advisers will clearly not be able to make any difference in that regard. Even air strikes are likely to lead to more civilian casualties.

Tikrit's residents have consistently told me over the past two weeks that helicopters have been bombing the city – with little to no evidence of militant casualties. Several residents described how helicopters bombed civilian vehicles as they lined up for fuel. The drive, it seems, is only getting longer.