The US faces a huge task in reversing a culture of "crazy conspiracy theories" that have exacerbated divides in the country, Barack Obama says.
In a BBC interview, the former president says the US is more sharply split than even four years ago, when Donald Trump won the presidency.
And Mr Obama suggests Joe Biden's victory in the 2020 US election is just the start of repairing those divisions.
"It'll take more than one election to reverse those trends," he says.
Tackling a polarised nation, he argues, cannot be left only to the decisions of politicians, but also requires both structural change and people listening to one another - agreeing on a "common set of facts" before arguing what to do about them.
However he says he sees "great hope" in the "sophisticated" attitudes of the next generation, urging young people to "cultivate that cautious optimism that the world can change" and "to be a part of that change".