MELBOURNE, Australia — If the United States had the same Covid death rate as Australia, about 900,000 lives would have been saved. The Texas grandmother who made the perfect pumpkin pie might still be baking. The Red Sox-loving husband who ran marathons before Covid might still be cheering at Fenway Park.

For many Americans, imagining what might have been will be painful. But especially now, at the milestone of one million deaths in the United States, the nations that did a better job of keeping people alive show what Americans could have done differently and what might still need to change.

Many places provide insight. Japan. Kenya. Norway. But Australia offers perhaps the sharpest comparisons with the American experience. Both countries are English-speaking democracies with similar demographic profiles. In Australia and in the United States, the median age is 38. Roughly 86 percent of Australians live in urban areas, compared with 83 percent of Americans.

Yet Australia’s Covid death rate sits at one-tenth of America’s, putting the nation of 25 million people (with around 7,500 deaths) near the top of global rankings in the protection of life.

Australia’s location in the distant Pacific is often cited as the cause for its relative Covid success. That, however, does not fully explain the difference in outcomes between the two countries, since Australia has long been, like the United States, highly connected to the world through trade, tourism and immigration. In 2019, 9.5 million international tourists came to Australia. Sydney and Melbourne could just as easily have become as overrun with Covid as New York or any other American city.

So what went right in Australia and wrong in the United States?

For the standard slide-show presentation, it looks obvious: Australia restricted travel and personal interaction until vaccinations were widely available, then maximized vaccine uptake, prioritizing people who were most vulnerable before gradually opening up the country again.

From one outbreak to another, there were also some mistakes: breakdowns of protocol in nursing homes that led to clusters of deaths; a vaccine rollout hampered by slow purchasing. And with Omicron and eased restrictions, deaths have increased.

But Australia’s Covid playbook produced results because of something more easily felt than analyzed at a news conference. Dozens of interviews, along with survey data and scientific studies from around the world, point to a lifesaving trait that Australians displayed from the top of government to the hospital floor, and that Americans have shown they lack: trust, in science and institutions, but especially in one another.

When the pandemic began, 76 percent of Australians said they trusted the health care system (compared with around 34 percent of Americans), and 93 percent of Australians reported being able to get support in times of crisis from people living outside their household.

In global surveys, Australians were more likely than Americans to agree that “most people can be trusted” — a major factor, researchers found, in getting people to change their behavior for the common good to combat Covid, by reducing their movements, wearing masks and getting vaccinated. Partly because of that compliance, which kept the virus more in check, Australia’s economy has grown faster than America’s through the pandemic.

But of greater import, interpersonal trust — a belief that others would do what was right not just for the individual but for the community — saved lives. Trust mattered more than smoking prevalence, health spending or form of government, a study of 177 countries in The Lancet recently found. And in Australia, the process of turning trust into action began early.

Government: Moving Quickly Behind the Scenes

Greg Hunt had been Australia’s health minister for a couple of years, after working as a lawyer and investor, when his phone buzzed on Jan. 20, 2020. It was Dr. Brendan Murphy, Australia’s chief medical officer, and he wanted to talk about a new coronavirus in China.

Dr. Murphy, a low-key physician and former hospital executive, said there were worrisome signs of human-to-human transmission.

“What’s your honest, considered advice?” Mr. Hunt recalled asking.

“I think this has the potential to go beyond anything we’ve seen in our lifetime,” Dr. Murphy said. “We need to act fast.”

The next day, Australia added the coronavirus, as a threat with “pandemic potential,” to its biosecurity list, officially setting in motion the country’s emergency response. Mr. Hunt briefed Prime Minister Scott Morrison, visited the country’s stockpile of personal protective equipment and began calling independent experts for guidance.

Sharon Lewin, the director of the Peter Doherty Institute for Infection and Immunity, one of Australia’s top medical research organizations, received several of those calls. She fed his questions into the meetings that had started to take place with scientists and officials at Australia’s public health laboratories.

“There was a very thoughtful level of engagement, with politicians and scientists, right at that early phase in January,” Dr. Lewin said.

The first positive case appeared in Australia on Jan. 25. Five days later, when the Centers for Disease Control and Prevention confirmed the first human transmission of the virus in the United States, President Donald J. Trump downplayed the risk. “We think it’s going to have a very good ending for us,” he said.

The same day, Mr. Hunt struck a more practical tone. “Border, isolation, surveillance and case tracing mechanisms are already in place in Australia,” he said.

Less than 24 hours later, on Feb. 1, Australia closed its border with China, its largest trading partner. On Feb. 3, 241 Australians were evacuated from China and placed in government quarantine for 14 days. While Americans were still gathering in large groups as if nothing was wrong, Australia’s Covid containment system was up and running.

A full border closure followed. Hotels were contracted to quarantine the trickle of international arrivals allowed in. Systems for free testing and contact tracing were rolled out, along with a federal program that paid Covid-affected employees so they would stay home.

For a business-friendly, conservative government, agreeing to the Covid-containment measures required letting go of what psychologists describe as “sticky priors” — longstanding beliefs tied to identity that often hold people back from rational decision-making.

Mr. Morrison trusted his close friend Mr. Hunt. And Mr. Hunt said he had faith in the calm assessments and credentials of Dr. Lewin and Dr. Murphy.

In a lengthy interview, Mr. Hunt added that he also had a historical moment of distrust in mind: Australia’s failures during the 1918 flu pandemic, when inconsistent advice and a lack of information sharing led to the rise of “snake oil” salesmen and wide disparities in death rates.

In February and March, Mr. Hunt said, he retold that story in meetings as a warning. And in a country where compulsory voting has been suppressing polarization since 1924, Australia’s leaders chose to avoid partisanship. The Morrison government, the opposition Labor Party and state leaders from both parties lined up behind a “one voice” approach, with medical officers out front.

Still, with a highly contagious virus, scientists speaking from podiums could do only so much.

“Experts ‘getting on the same page’ only matters if people actually trust the actions government is taking, and trust their neighbors,” said Dr. Jay Varma, director of Cornell’s Center for Pandemic Prevention and Response and a former Covid adviser to Mayor Bill de Blasio of New York.

“While that type of trust is relatively higher in New York City than in other parts of the U.S.,” said Dr. Varma, who has worked extensively in China and Southeast Asia, “I suspect it is still quite low compared to Oceania.”