Looking back at the past two decades since the US invasion of Iraq in March 2003, foreign policy experts warn that Washington has learned few lessons since then, and the lack of accountability for the war's proponents has created an environment where a similar American-led war could occur.

"My basic answer to the question of 'could it happen again?' is for sure, absolutely it could happen again," Ahsan Butt, an associate professor at George Mason University, said during a panel hosted on Thursday by the Cato Institute in Washington.

"The real lessons of the Iraq war really haven't been learned."

In the leadup to the US invasion of Iraq, top officials in the American government, including former President George Bush, said that Saddam Hussein was in possession of weapons of mass destruction (WMDs).

They cited US intelligence, including on the basis of information from a now-discredited Iraqi opposition group, which turned out to be false. Nevertheless, Washington launched an invasion with little opposition from Congress, leading to a war that killed hundreds of thousands of people in Iraq, and later in Syria.

And leading up to the invasion, there was near unanimous support for the war in Washington, with few news outlets - with the exception of Knight Ridder - pushing back against the links between Iraq's Hussein, WMDs, and al-Qaeda.

The Cato Institute was one of the few think tanks in the US to push back against the US invasion, and for doing so was slammed with criticism and censure from Washington's circle of foreign policy experts.

But individuals like Bush, former deputy defence secretary Paul Wolfowitz, former secretary of state Condoleeza Rice, and many others who supported the war efforts, did not face any consequences for their mistakes nor did their reputations suffer.

"We have to be honest that the worst advocates, cheerleaders and purveyors of the worst lies of the Iraq war have not been held accountable. They continue to exercise outsized influence in most of our key institutions and the media," said Don Caldwell, vice president of the Center for Renewing America and a veteran of the Iraq War.

"The worst thing though, is the fact that there has not been a repudiation of the mindset that led us to the war in Iraq."

Partisan polarisation

According to the Pew Research Center, 66 percent of Americans said they believed that Saddam Hussein was involved in the 9/11 attacks on the World Trade Center and the Pentagon. In April 2003, more than 70 percent of Americans polled said that the US was right in going to war in Iraq.

"I think that's the median voter's position that this is a reasonable idea badly executed, not a bad idea. And so I think that's another big reason why something like this could happen relatively soon and relatively easy because no one's actually dealt with the implications of why the US went into Iraq," Butt said.

However, the experts noted that in the past two decades, several factors have changed in the US that help to create more opposition to US policy decisions.

One is that the US political landscape is more partisan than it was in 2003, which makes it more difficult to come to unanimous decisions about going to war.

"Generally partisan polarisation is sort of this, quote-unquote, bad thing in the US," Butt said.

"But I think when it comes to starting dumb or idiotic or aggressive wars, it's probably a good thing because it's hard for any one leader or any one president, any one cabinet to have that bipartisan support you need in this country that was quite common in the 2000s."

Caldwell also noted that there are many more institutions in place in Washington that would push back against the drums of war.

"You have more scholars spread across more centres and institutions and academia and in the policy space on both the right and left and I think that is a positive development," Caldwell said.

However, the ability of the president to go to war without the approval of Congress was established in the wake of the 9/11 attacks and the later invasion of Iraq. There are several authorisations for the use of military force (AUMF) currently in place, including the 1991 AUMF passed during the First Gulf War, the 2001 AUMF passed after the 9/11 attacks, and the 2002 AUMF for Iraq.

While Congress is moving closer towards shuttering the 1991 and 2002 AUMFs, the wider-ranging 2001 authorisation remains on the books and gives the White House extensive authority to go after anyone linked to the perpetrators of the 9/11 attacks.

According to Sumantra Maitra, a senior editor at The American Conservative, the worldview and framework of many in the current Biden administration is not far from that of the Bush administration. US President Joe Biden himself, then as a senator, spoke of war with Iraq several years before the invasion.

"The calculation of the worldview of this administration is not very different from the previous administrations," Maitra said during the panel at Cato.