Its new president and vice-president arrive while Americansare well outside their comfort zones - and the new leaders can use this time to make important changes.
Bringing the pandemic under control and tackling other problems requires a massively scaled-up effort. And it's harder to do that once people have slipped back into a more "normal" mindset.
Lights surround the Lincoln Memorial Reflecting Pool, placed as a memorial to Covid-19 victims in Washington, with the US Capitol in the background. Photo / AP
Aside from the health emergency, the economy needs to be bolstered - in ways that will make it more resistant to future disasters and able to deal with climate change.
Biden and Harris are a well-balanced pair who seem suited to difficult tasks - both have been through testing times in the past - and who know about loss. For both, their big day was bittersweet: Biden's son Beau and Harris' mother Shyamala were not alive to see them triumph.
After the past four years, an administration that promises to be more straightforward, competent and focused on helping the public will seem like a breath of fresh air.
There are some small signs that the country may take this chance to pick up the pieces and set off on a different path.
Key Republicans – former vice-president Mike Pence, and congressional leaders Mitch McConnell and Kevin McCarthy – stepped away from Donald Trump at the end.
It was too little, too late, after they failed to constrain the former president over his false claims of a "stolen" and "rigged" election, which ultimately spiralled into the mob attack two weeks ago on the US Capitol. There's a stink of hypocrisy. No doubt the parties will clash over Biden's programme.
But it still matters that McConnell on Wednesday bluntly stated that Trump sparked the Capitol assault. The Republican Senate leader said: "The mob was fed lies. They were provoked by the President and other powerful people."
Biden invited McConnell and McCarthy, the Republican House leader, to join him at an inauguration morning Mass, with the Congressional Democratic leaders. Pence attended the swearing-in. A group of 17 new House Republicans sent a letter congratulating Biden and saying they "hope to work" with him.
The handover ceremonies demonstrated how quickly and heavily the focus shifts to today's leader from yesterday's. Biden is now the centre of power.
For the Republican leadership to steer members away from Trumpism, they need to be heard to acknowledge the failings of the party, administration and its leader. The former president remains popular within the party.
The US has now lost more than 400,000 people to the virus and the first memorial it has held for the victims was a simple but authentic inauguration ceremony by the Reflecting Pool.
"To heal we must remember," Biden said. "It's hard sometimes to remember. But that's how we heal. It's important to do that as a nation."
Yesterday he said America had much to repair, heal and gain.
America's politics and society looks broken down. The scenes of troops in camouflage patrolling the streets of Washington reflect one of America's darkest moments. It could easily get worse.
But it's hard at an inauguration not to feel stirrings of hope, even with fluttering flags representing non-existent people and a parade without watching crowds.
