Hillary Clinton seized the opportunity presented by Sunday’s 21st anniversary of the September 11 terrorist attacks on New York and Washington to make a thinly-veiled attack on the extremism and divisiveness stoked by Donald Trump, as she called for a return to national unity.

The former US secretary of state and first lady invoked the bipartisan mood of the country in the wake of the 9/11 attack in which almost 3,000 people were killed.

“We were able to come together as a country at that terrible time, we put aside differences. I wish we could find ways of doing that again,” she told CNN in and interview for the State of the Union politics show on Sunday morning.

It was recalled how, as a Democratic US Senator for New York, in 2001 she flew over the burning wreckage of the World Trade Center at the disaster zone known as Ground Zero, in lower Manhattan, and went on air to pledge her unswerving support for Republican president George W Bush’s efforts to lead the US response.

Clinton noted that she met with Bush and asked for $20bn in federal funds to rebuild. “And he said ‘You got it’,” she told CNN anchor Dana Bash.

Clinton’s lament for the passing of such national togetherness then led her to make an impassioned attack on the turn towards extremism in American politics, albeit without mentioning Trump, the former Republican president who may yet run again in 2024, by name.

She said that 9/11 reminded Americans “about how impossible it is to try and deal with extremism of any kind, especially when it uses violence to try to achieve political and ideological goals”.

In another implicit reference to Trump’s Make America Great Again (Maga) rightwing movement, she went on to say that a “very vocal, very powerful, very determined minority wants to impose their views on the rest of us. It’s time for everybody, regardless of party, to say no, that’s not who we are as America.”

Clinton’s remarks came on the morning that the US marked 21 years of the al-Qaida attacks on the twin towers in New York City and the Pentagon in Washington, as well as Flight 93, the hijacked plane that crashed into a field in Shanksville, Pennsylvania. Joe Biden laid a wreath at the Pentagon, where he recalled that “terror struck us on that brilliant blue morning” but did not destroy “the character of this nation that terrorists sought to wound”.

Biden, who lost his first wife and their daughter to a car crash that also injured their two sons, then later lost one of those sons, Beau, to cancer, said: “I know for all of you who lost someone that 21 years is a lifetime and no time at all.”

The US president was joined in the pouring rain by General Mark Milley, chairman of the joint chiefs of staff, and defense secretary Lloyd Austin, who spoke about “a day of horror and loss” as 2,977 people were killed by the impact of the four passenger jets hijacked by the terrorists.

First lady Jill Biden led commemorations at the memorial site in Shanksville, accompanied by her sister Bonny Roberts, whom Biden initially feared she might have lost that day as she was a flight attendant for United Airlines, which suffered two of the hijackings, but, it turned out, was not flying that morning.

Kamala Harris and the second gentleman, her husband Doug Emhoff, joined the observance at the National September 11 Memorial in New York.

The vice-president did not speak, as per tradition, allowing the commemoration to be led by the reading of the names of those who died and moments of silence to mark the points when the hijacked planes struck each of the towers.

But in an interview with NBC’s Meet the Press, aired on Sunday, she spoke of America’s reputation as a world role model for democracy being under threat.

She cited challenges from the right wing to election integrity, including the attack on the US Capitol on January 6, 2021, in a bid to overturn Donald Trump’s defeat by Joe Biden, and extremist Republicans’ unwillingness to condemn it, while also fielding many candidates in current elections who still refuse to accept the true result.

“I think it is a threat…it is very dangerous and I think it is very harmful. And it makes us weaker,” she said.

She added that when meeting foreign leaders, the US “had the honor and privilege historically of holding our head up as a defender and an example of a great democracy. And that then gives us the legitimacy and the standing to talk about the importance of democratic principles, rule of law, human rights….through the process of what we’ve been through, we’re starting to allow people to call into question our commitment to those principles. And that’s a shame.”

On Sunday, Kevin McCarthy, the Republican minority leader in the US House of Representatives, slammed the Biden administration.

“Twenty one years ago, we had a commander-in-chief [George W Bush] who united the country rather than divided the country,” McCarthy told Fox News. He said were the Republicans to take back control of the House in November’s midterm elections, “we would build a nation that is safe. We have watched Democratic policies make it the deadliest of America (sic) in the last 20 years.”