In short:

Outgoing US ambassador Caroline Kennedy has delivered a farewell address at the National Press Club, seeking to reassure Australians about the implications of a second Trump presidency for the alliance and climate policy.

The ambassador also criticised her cousin Robert F Kennedy Jr, Trump's pick for health chief, for his vaccine scepticism.

What's next?

The ambassador will depart Canberra within weeks.

The outgoing US ambassador Caroline Kennedy has tried to reassure Australia about the implications of a second Trump presidency, while declaring that the Albanese government's nuclear-powered submarine plan is an "existential investment in Australia's sovereignty."

The ambassador also criticised the vaccine scepticism embraced by her cousin Robert F Kennedy Jr, who Donald Trump has tapped to be the head of the US health agency, labelling her cousin's views "dangerous".

Ms Kennedy made the remarks during a wide-ranging speech at the National Press Club, just weeks before she departs from Canberra.

She was peppered with questions about Trump's trade, climate, security policies and cabinet picks, including Mr Kennedy, who has been criticised for spreading misinformation and making false claims about vaccines.

Cousin's views 'dangerous'

"I think Kennedy's views on vaccines are dangerous, and I don't think most Americans share them," she said.

The ambassador said that included other members of the Kennedy family, who were "united" in support of the medical system.

"My uncle Teddy [Kennedy] spent 50 years fighting for affordable health care in the Senate and it's something that our whole family is so proud of, that President Obama signed the Affordable Care Act and built on the work that my uncle had done over many years," she said.

"I would say that our family is united in terms of our support for the public health sector and infrastructure, and has the greatest admiration for the medical profession in our country.

"Bobby Kennedy has got a different set of views."

There are deep anxieties in Canberra over some of the president-elect's other cabinet picks, including former Democratic congresswoman Tulsi Gabbard, who has been tapped as director of national intelligence despite accusations that she has spouted Kremlin propaganda.

The ambassador stressed there were "thousands of people" working in US intelligence agencies and suggested the Senate might block many of Trump's nominees.

"Let's just calm down and wait and see what happens," she said.

"Obviously that would be of great concern [but] we'll see who actually gets confirmed."

AUKUS 'existential' for Australia's sovereignty

Ms Kennedy also delivered a forceful defence of AUKUS, and brushed off questions about whether the huge price tag to deliver nuclear-powered submarines could be justified, pointing to Chinese aggression in the region.

"To those who still question whether AUKUS is necessary, ask the Philippines and Vietnam what it's like to have your ships rammed and sunk by Chinese 'coastguard' vessels, or Japan what happens when missiles land close to shore," she said.

"AUKUS is an existential investment in Australia's sovereignty and way of life, and you can't put a price on that."

There are also deep concerns in Canberra about the implications of Trump's broader trade and climate policies, including fears that his plan to massively ramp up tariffs on Chinese goods could spark a global trade war.

It is not yet clear if Australia will be able to negotiate an exemption from Trump's declaration to massively expand tariffs on all exports to the US.

Ms Kennedy said she could not predict what the Trump administration would do, but suggested Australia had a strong case to mount for an exemption, pointing to Malcolm Turnbull's successful efforts to protect Australia from steel tariffs in 2018.

"There's a lot of things that get said in the campaign but I think that if you look at the positive side of it … you'll see that I think Australia has a very privileged position, and that's because we work so closely together across the board," she said.

'No turning back' on climate even if Trump pulls out of Paris

The ambassador also suggested that global momentum on the clean energy transition would make it difficult for the Trump administration to seriously disrupt cooperation on climate change — despite the president-elect's promise to unwind green subsidies and pull the US out of the Paris Agreement.

"The green energy transition is underway. The private sector supports it. There's no turning back," she said.

"Our work in critical minerals, which started under the first Trump administration, is going to continue and become increasingly necessary. It fits with our geopolitical assessment but it also is critical to addressing climate.

"There are plenty of areas at which we can continue to cooperate to address this challenge. Maybe not as fast or in different ways, but … I think the work is going to continue even if it changes some emphasis."