America’s strident political divisions have become the greatest threat to its own survival, Susan Rice, former national security adviser has warned in a new book, in which she also reveals the degree to which those divisions have threatened to fracture her own family.

Rice, the most senior African American woman in the Obama administration, became a hate figure for the American hard right – sometimes on issues for which she had little responsibility. In her new memoir, Tough Love, she describes her anxiety as her son Jake drifted to the other end of the political spectrum, becoming the leader of a Trumpist Republican student organisation at Stanford University.

“We’ve made a very conscious decision,” Rice said in an interview with the Guardian at her office at American University in Washington. “It’s not one that’s easy, that we don’t have to work at every day and it’s sometimes painful. But we have made a very conscious decision to put what binds us our love as a family, our history, our aspirations, far above our political and policy differences.”

Rice admits that a happy ending, in her family and in the nation at large, is not a foregone conclusion. In Tough Love, the personal and the political intertwine constantly, but never more painfully than after she left office in January 2017 and her relationship with Jake begins to mirror the increasingly extreme polarisation in US politics.

She describes “explosive, sometimes profane, arguments” with her son, expressing her fear that “there could come a day when Jake and I determine that our disagreements have become so profound that we are irreconcilable”.

The familial rift between mother and son made national news in October last year, when she was threatening to run for a Senate seat in Maine, after the incumbent Republican, Susan Collins voted to confirm Brett Kavanaugh as a supreme court justice in the face of evidence of he had been involved in sexual assault. (She later decided against a run for family reasons, but does not rule out elective office in the future.)

Meanwhile, Jake Rice-Cameron (the eldest child of the former national security adviser and her husband Ian Cameron, a former ABC News executive producer, who she met at university), was hosting an event at Stanford celebrating Kavanaugh’s confirmation, where he claimed to have been assaulted by a female student with differing views.

Barack Obama, Susan Rice and David Cameron look on during a scenario-based policy discussion of the 2016 Nuclear Security Summit. Photograph: Alex Wong/Getty Images

A Facebook page for his Republican group in May 2018 declares its intention to “Make Stanford Great Again”. Its agenda is laid out as: “Trump is great. Build the wall. Deport criminal illegal immigrants. Guns save lives. There are only two genders. Abortion is murder … Taxation is theft. Affirmative action is racist. White privilege is a lie.”

It is hard to imagine a manifesto more diametrically opposed to everything Susan Rice has spent her adult life believing in and fighting for. She said that his current views (they had dinner together three days before the interview) were more nuanced.

“I think he’s got very mixed feelings about Trump,” she said, while stressing she did not want to speak for him. “He characterized himself as a Reagan conservative. That’s very different in my appreciation from a Trump conservative. He’s an internationalist, and he believes in strong US leadership, he believes in our alliances. He and I have a very similar conception of where the threats and challenges lie.”

Much of the Republican party, on paper at least, could be described in similar broad terms. But in practice, it has shown itself loyal to Trump, even as he tramples on almost everything they have traditionally held dear, leaving the country hostage to a volatile and self-dealing leader.

“Today our domestic political divisions constitute the greatest threat to our national security,” Rice argues in her book. That is in part because of the unlimited role of big money in politics, partly because of relentless gerrymandering of congressional districts, but also because “our adversaries have demonstrated both the will and capacity to weaponise our divisions to use against us”.

The US is making it easy for its enemies “because we now have a leader in the White House whose express intent is to exacerbate those divisions”.

“We never had a president before who actively demonizes large segments of the population. And who denigrates the freedom of the press and the institutions of the state that are there to serve him and the country.” Rice said.

At the end of 2016, she had an inside view of just how different the Trump administration was going to be than anything Washington had ever seen. After the shock election result, Rice and her national security council team prepared over a hundred briefing papers on the administrative and policy challenges her successor, former defence intelligence chief Michael Flynn, and his deputy, the Fox TV pundit KT McFarland, might have to face.

Susan Rice, shakes hands with Michael Flynn, during the 2017 Passing The Baton conference at the United States Institute of Peace. Photograph: Mark Wilson/Getty Images

But they seemed curiously detached and uninterested. McFarland stunned the outgoing staff by turning up to meetings in a full-length mink coat and then asking whether she and Flynn could share the job, with Flynn doing mornings and her doing the afternoons.

It took Rice two or three weeks to persuade Flynn to meet. When they finally did, he did not seem interested in all the nuts and bolts of running the national security council staff and coordinating principals meetings. She doubts any of the briefing papers she provided were ever read. Instead, Flynn was “bizarrely focused on exotic, highly compartmented, classified matters, which I did not think he needed to know until after he took the job”.

Rice refuses to say any more on what secrets Flynn was trying to pry out of her, saying only she had grave doubts he would survive long in the job. She was right. He resigned within a month, after it emerged he had given a misleading account of his exchanges with the Russian ambassador. McFarland left two months later.

Trump is now on his fourth national security adviser, but the intricate machinery of White House policymaking, mediating the views of the government agencies, has withered away, Rice argued.

“It’s completely broken down,” she said. “It doesn’t, for the most part, exist.”

Even if Trump is defeated in a year’s time, she said it would take more than the next presidency for the nation to regain its footing on the world stage.

The country has gone through worse, more violent, periods of division in its turbulent history and emerged stronger as a result, Rice insists. Faith and willpower will conquer, she argues, in the nation as well as in the Rice-Cameron household. But that optimism assumes there is not a second Trump term.

“It’s such a nightmare scenario, in terms of our global posture and leadership, I can’t even … I don’t want to think about it.”