Dr. Anthony Fauci, the nation's top infectious diseases expert, said political polarization contributed to the high coronavirus death toll in the U.S. - and that the country should have never reached 500,000 deaths.
Fauci said in an interview with Reuters on Monday that wearing masks became a "political statement" instead of a public health precaution.
"Even under the best of circumstances, this would have been a very serious problem," Fauci said. "However, that does not explain how a rich and sophisticated country can have the most percentage of deaths and be the hardest-hit country in the world. That I believe should not have happened."
The U.S. has more COVID-19 cases than any other country in the world, and on Monday, surpassed 500,000 deaths, according to Johns Hopkins University. As of Tuesday, the U.S. has reported more than 28 million coronavirus cases.
Fauci also pointed to the states and cities that disregarded re-opening recommendations by former President Donald Trump's White House Coronavirus Task Force.
Fauci said the disregard was "incomprehensible to me [when] you could see right in front of your eyes what was happening."
"When the American spirit is so divided, that really, really made me sad," he added.
Fauci's comments were echoed by National Institutes of Health Director Francis Collins, who said "the evidence was pretty compelling by last March or April that uniform wearing of masks would reduce transmission of this disease"
"And yet, with a variety of messages through a variety of sources," he told Axios, "mask wearing became a statement about your political party or an invasion of your personal freedom."
During his time in office, Trump said wearing masks was "voluntary" for Americans - and that he didn't think it fit with his role as president.
"I just don't want to be doing - somehow sitting in the Oval Office, behind that beautiful, Resolute Desk, the great Resolute Desk, I think wearing a face mask - as I greet presidents, prime ministers, dictators, kings, queens, I don't know, it somehow, I don't see it for myself," Trump said.
Trump also took aim at now-President Joe Biden for his frequent mask wearing in the run-up to last year's presidential election.
"I don't wear masks like him. Every time you see him he's got a mask. He could be speaking 200 feet away and he shows up with biggest mask I've ever seen," Trump said of Biden during a 2020 presidential debate.
In an interview with "Good Morning America" on Monday, Fauci - now Biden's chief medical advisor in the White House - urged Americans to "go forward and be completely committed as a unified country to just go at this together." Biden has called for 100 days of mask wearing during the beginning of his presidency to curb the spread of the coronavirus.
Fauci also said "we cannot declare victory" just because daily coronavirus cases have decreased.
"We have variants out there that could actually set us back," he said.
Variants from the U.K., Brazil and South Africa "seem to spread more easily and quickly than other variants," which could lead to an increase in cases that "put more strain on health care resources, lead to more hospitalizations and potentially more deaths," according to the Centers for Disease Control and Prevention.
Biden has suggested life could return to "normal" by Christmas, CNN reported.
"As my mother would say, with the grace of God and the goodwill of the neighbors, that by next Christmas I think we'll be in a very different circumstance, God willing, than we are today," Biden said last week. "A year from now, I think that there'll be significantly fewer people having to be socially distanced, having to wear a mask."