The summer that was supposed to mark the United States' independence from COVID-19 is instead drawing to a close with the U.S. more firmly under the tyranny of the virus, with deaths per day back up to where they were in March.

The delta variant is filling hospitals, sickening alarming numbers of children and driving coronavirus deaths to the highest levels of the entire pandemic in some places. School systems that reopened their classrooms are abruptly switching back to remote learning because of outbreaks.

Legal disputes, threats and violence have erupted over mask and vaccine requirements. The U.S. death toll stands at more than 650,000, with one major forecast model projecting it will top 750,000 by Dec. 1.

"It felt like we had this forward, positive momentum," lamented Katie Button, executive chef and CEO at two restaurants in Asheville, North Carolina. "The delta variant wiped that timeline completely away."

It wasn't supposed to be this way. More than six months into the U.S. vaccination drive, President Joe Biden held a White House party on July 4 to celebrate the country’s freedom from the virus, and other political leaders had high hopes for a close-to-normal summer. Then the bottom fell out. Biden recently faced scrutiny as many say he failed to achieve the end of the pandemic until autumn. Now he is expected to enter the fall season with a push for new vaccine mandates and broader testing programs. The Biden administration was expected to unveil the six-prolonged plan Thursday after the American leader received a briefing in the Oval Office on new steps against COVID-19 a day before.

According to CNN, the plan will be focused on inoculating unvaccinated citizens and protecting those with jabs through booster shots. Other issues the country faces are keeping schools open, mandating masks, promoting testings, economic recovery and increasing the care quality. A source familiar with the matter told CNN that Biden would specifically press on making vaccination for citizens a requirement, including mandating inoculation for federal workers. He also would push businesses to mandate jabs for employees.

"We've always said we would build on what we've announced to date," press secretary Jen Psaki told reporters, citing current mandates for U.S. military service members and federal health care workers. "We also believe the private sector has a role here."

The confidence for Biden's approach against COVID-19 has rapidly sagged due to the recent spike of coronavirus infections. The poll conducted by The Washington Post and ABC News indicated that 52% of respondents approved the U.S. administration's handling of the pandemic at the end of August, which is 10 points less than in June. His popularity also has been frayed by the chaotic American withdrawal from Afghanistan, which led to the Taliban's takeover of the whole country in a short period of time. Biden claimed that the U.S.-led 2001 intervention in Afghanistan was never about nation-building, but simply the mission for the assassination of Osama bin Laden, the leader of terrorist group al-Qaida whom the U.S. accused of staging a deadly attack on World Trade Center in New York City on Sept. 11, killing over 3,000 people and injuring even more.

ABC News polls showed that 47% rate their risk of coronavirus as moderate or high, 18 percentage points higher than at the end of June. Fears of getting infected with the virus among adults who received one or two vaccine shots have skyrocketed from 32% to 52%, while concern among unvaccinated adults has risen from 22% to 35% over the same period.

The summer wave was fueled by the extra-contagious delta variant combined with stark resistance to vaccinations that formed along political and geographic lines, said Dr. Sten Vermund of the Yale School of Public Health.

"The virus was more efficient in spreading among the unvaccinated so that you blunted the expected benefit of vaccines," Vermund said.

The crisis escalated rapidly from June to August. About 400,000 COVID-19 infections were recorded for all of June. It took all of three days last week to reach the same number. The U.S. recorded 26,800 deaths and more than 4.2 million infections in August. The number of monthly positive cases was the fourth-highest total since the start of the pandemic.

The 2021 delta-driven onslaught is killing younger Americans at a much higher rate than previous waves of the pandemic in the Northeast last spring, the Sun Belt in the summer of 2020 and the deadly winter surge around the holidays.

During the peaks of those waves, Americans over 75 suffered the highest proportion of death. Now, the most vulnerable age group for death is 50 to 64, according to data from U.S. officials. Overall, the outbreak is still well below the all-time peaks reached over the winter, when deaths topped out at 3,400 a day and new cases at a quarter-million per day.

The U.S. is now averaging over 150,000 new cases per day, levels not seen since January. Deaths are close to 1,500 per day, up more than a third since late August. Even before the delta variant became dominant, experts say that larger gatherings and relaxed social distancing measures were fueling new cases.

"We had been cooped up for over a year, and everyone wanted to get out," said Dr. David Dowdy, a public health researcher at the Johns Hopkins Bloomberg School of Public Health. "In the face of that kind of strong change in behavior, even getting almost two-thirds of our adult population vaccinated wasn’t enough."

The COVID-19 vaccines remain highly effective against hospitalization and death, but tens of millions of eligible Americans remain unvaccinated. Nearly 40% of Americans 12 and older are not fully protected.

In Rapid City, South Dakota, school officials have recorded nearly 300 cases among students and staff since classes began less than two weeks ago. Still, most school board officials voted this week 5-2 against a proposed two-week mask mandate.

"Nobody wanted to be here. Everyone wanted the personal freedom to be away from masks and free of illness," said Amy Policky, who introduced the proposal with one other member. "But we have to look at the facts: We’re having illness rage through the school and the community, so what can we do?"

Still, Yale's Vermund sees reasons to be cautiously optimistic about the next few months. Cases in most states appear to be plateauing and are likely to decline in the fall, buying health authorities more time to vaccinate adults and teenagers before flu season.

"If we can continue making progress between now and Thanksgiving, we may be able to substantially blunt the coronavirus surge in flu season," Vermund said.

While the economy has been rebounding strongly over the past several months, hiring slowed sharply in August in a sign that the variant is discouraging Americans from flying, shopping or eating out. And on Monday, unemployment benefits – including an extra $300 a week from the federal government – ran out for millions of Americans.

Button, the North Carolina chef, was feeling great heading into the summer. Her team was mostly vaccinated in May, and restrictions were loosening. But the crisis soon changed direction. Button supports the mask mandate that was recently reinstated in her county but said her employees are exhausted by having to enforce it. And since she has no outdoor seating, some diners have been less comfortable coming in.

"It’s hard to take a step forward and then take three steps back," she said.