When Prime Minister Jacinda Ardern arrived at the Capitol Building in Washington DC on Thursday, the flags were at half-mast.

The shootings at Robb Elementary School in Texas that took the lives of at least 19 children and three adults had taken place the day before Ardern was due in DC to meet with a raft of Senators on her US trip.

That appears to have stalled an expected announcement on whether Ardern was set to have a meeting with US President Joe Biden - but Ardern said she hoped to have an update on that shortly.

That meeting is still expected to take place and gun reforms may well be added to the agenda after Biden's initial response was to promise further reforms would be coming.

It was certainly one of the main topics US Senators raised in their comments ahead of meeting Ardern, with some saying there were lessons they could take from New Zealand despite the obvious differences between the two countries on the matter.

When her visit was planned, Ardern had expected to be talking about the US Indo-Pacific strategy, pushing the case for the US to get back into the CPTPP trade deal and possibly China's move to try to persuade Pacific Island leaders to sign up for a trade, defence and security agreement.

She had not expected to find herself in the US debate around gun reforms. However, one of the reasons Ardern is known in the US is because of her handling of the aftermath of the terror attacks on mosques in Christchurch in 2019 – and the swift action to ban mass assault rifles afterwards.

Ardern's first meeting was with the 35-year-old Democrat and Georgia Senator Jon Ossoff, who has a photo of Martin Luther King Jr on his wall and delivered a heartfelt message about the shooting when meeting Ardern. Ardern nodded as he talked about his baby daughter Eva and how he prayed for her safety.

"I know the Prime Minister after the tragic massacre in Christchurch, demonstrated the kind of leadership that we need to see in this country right now. I'm probably the only member of the Senate who grew up during a time when these kinds of attacks in schools were routine. We cannot let this be what passes for normal in America."

Ardern's next port of call was Republican and Ohio Senator Mitt Romney. His photo op was in front of movie posters of John Wayne and Roy Rogers.

He said little until he was asked if he would support gun reforms – Romney has taken donations from gun lobby groups.

He replied that he did support some reform – specifically the so-called 'Red Flag' measures which allow guns to be removed from people considered to be a risk to themselves or others. Variations of such laws exist in about 19 US states.

A third comment was made by Senator Rick Larsen, who is also the co-chair of the Friends of New Zealand caucus. Larsen asked what it would take for Congress to do more – but was pessimistic about the chances of significant change.

"We can't tolerate this reality where we normalise the murder of elementary school children, or patrons of a grocery store in Buffalo, or a movie theatre, a church, a nightclub or a concert. It can't be normal."

The Democrat senators all noted the action New Zealand had taken and what the US could learn from that. But Larsen also sounded a note of caution about the need for the US to sort it out for itself. He acknowledged other countries might wonder why the US would not act – and said people within the US were thinking the same.

"This is a United States domestic issue and it's probably not in the best interests of other countries' leaders to come out and openly help us with our business. Just as vice versa, it wouldn't be helpful for the US – even though we are really good at it – to interfere in a very important domestic issue [elsewhere]."

Ardern will be wary of wading into that political debate – but it is a tightrope walk on such a contentious issue in the US. Ardern said she had been happy to answer their questions. "It's not for me as a leader of a nation with different histories and experiences to tell other nations what they should or should not do. All I can do is reflect that New Zealand had its own horrific experience and made changes as a result."

She said to Ossoff that while she accepted every country was different, t had happened in New Zealand because the public had wanted it. She did not add any comment on various polls showing the US public also wanted it.

"I can only reflect on our experience, but if there's any message that I can share from that and take what you will from it, I believe change is possible.

Even on the most difficult of political issues, when you have will amongst your people, then change is possible."

Ardern said her talks with the Senators had been useful and spanned the role of China in the region, trade, the Christchurch Call and the Ukraine war.

She had also been taken with the New Zealand links of some of the Senators, although Ossoff committed an inadvertent blunder when he said that one of his family lived in Australia, which was close to New Zealand, getting a laugh out of Ardern.

Larsen knew all about the Kawakawa public toilets because one of his wife's relatives was Friedensreich Hundertwasser.

Ardern is now in Boston, preparing to deliver the Harvard University Commencement Address in the early hours of Friday morning New Zealand time.

Ardern said several senators had raised that with her and admitted to some trepidation about it - but would not give any clues as to what she would talk about.

One of the reasons Harvard selected Ardern for the honour was because of her handling of the aftermath of the Christchurch mosque attacks.