(CNN) The coronavirus emergency is fast transforming into one of the gravest political and societal challenges of the modern age -- and America's leaders are only just beginning to understand the gargantuan task before them.

The longer-term realities are setting in for Americans amid calls for a World War II-style national mobilization to fight the pandemic. And the deeply concerned politicians charged with fighting it are comparing the historic significance of the crisis to the 1918 influenza calamity, the Great Depression and 9/11.

But it is not clear if the stark message is getting through to everybody, especially younger Americans, who are vital to stopping a disease now spreading like wildfire before it reaches levels that could overwhelm the US health system.

In San Francisco, for instance, people were seen strolling, skating and cycling -- despite a shelter-in-place order meant to keep people at home except for essential errands. Experts warn that while young people are typically spared the worst complications of Covid-19, they can spread the virus to older and more vulnerable people.

Amid signs that the coronavirus drama will be longer, more expensive and more taxing on the country's human tolerance than expected, the White House is seeking extraordinary power to stop the economy from going over a cliff. A massive $1 trillion stimulus plan -- including $1,000 checks for most Americans -- is larger than the Recovery Act that helped pull the country out of the Great Recession.

There are some encouraging signs of a common cause between the federal government and states and local jurisdictions. But there are few answers from the White House on the most critical looming challenge: a shortage of protective equipment for medical staff and breathing machines and intensive care unit beds ahead of a coming surge of patients.

President Donald Trump , who has fractured truth and carved deep political divides over a turbulent three years in office, now faces one of the most profound challenges of any recent Oval Office holder. His every word is being watched for evidence that he is up to the challenge of fighting an enemy that did not devour the territory of US allies or rain terror on Americans, but is proliferating unseen among the population.

"We have to fight that invisible enemy," Trump said Tuesday, as more than 1,500 new cases of coronavirus came to light, the death toll topped 100 and the virus embedded into every US state.

Trump continued to bemoan negative news coverage Wednesday morning but said he would hold a news conference later in the day to announce "very important news" from the Food and Drug Administration related to the virus.

Dr. Anthony Fauci , the nation's top infectious disease specialist, said it could be weeks before he knows whether increasingly strict self-isolating regimes will flatten the curve of infections below a level that could collapse the public health care system. His comment was an alarming one because it underscored that the economy is not just going to endure a shutdown of a few weeks but will remain idle for job-killing weeks and maybe months.

'Massive collapse of the economy'

Bars, coffee shops, restaurants and theaters are closing down or offering curbside takeout service. Airlines are slashing capacity. Department stores are going dark, removing the lifeblood of an economy that was on a hot streak.

"We are seeing a massive collapse in the economy in this country," Sen. Jeff Merkley, an Oregon Democrat, told CNN.

Mnuchin lobbied Republican senators to first pass an earlier House relief bill before getting to a new urgent request for the $1 trillion stimulus package.

"It is a big number," he said. "This is a very unique situation in this economy."

Trump kept up his freshly statesmanlike pose, returning the compliment after one of his political foes, New York Gov. Andrew Cuomo, praised his leadership. But the President and his team also made efforts to rewrite the history of his previous attempts to play down the seriousness of the virus.

"I felt it was a pandemic long before it was called a pandemic," the President said of a virus he had previously argued was less of a problem than the regular flu and that could just go away.

While there were new signs that the White House was gearing up its mitigation program -- in terms of testing, economic repair work and calls for industry to donate masks to health care workers -- the effort still seemed short of what was needed.

Rhode Island Gov. Gina Raimondo said that while the previously laggard testing situation was improving, she was frustrated that she could not get answers from the federal government on when she would get more swabs for use in diagnosing patients.

"The good news is they are taking it urgently, more recently," Raimondo said. "But the action isn't there. And they really need to step up the response and give states what we need in order to fight the crisis on the front lines," she told CNN's Wolf Blitzer.

Cuomo laid out another dimension of the gathering storm, warning of a critical shortage of hospital beds. He said New York state would need up to 37,200 intensive care beds but currently only had 3,000. He also asked retired nurses and doctors to answer the call for help.

Such shortages are one reason federal and state leaders are pleading with residents to self-isolate, to limit the chains of infections associated with the coronavirus.

"Let's all be responsible and cancel things that we can cancel to really free up hospital beds and space," said Dr. Deborah Birx, a top member of the White House coronavirus task force.

"And then let's do everything that we can to ensure that we don't need the ventilators, because we protected the people who would have needed to use them," she said.

'Weeks' before officials know if anti-virus efforts are working

But Fauci was unable to give a firm fix on when it would become clear if the mitigation efforts were working and when he could predict how long the pandemic would last.

"It probably would be several weeks and maybe longer before we know whether we're having an effect," Fauci said.

For much of Tuesday, as news of stunning evidence of the virus's spread and its economic cost mounted, political leaders struggled to encapsulate the magnitude of the challenge.

"Remember those snow globes when you were a kid and you shook the globe and the snow went all over and the whole picture changed as soon as you picked up and shook that snow globe?" Cuomo asked.

"Somebody picked up our country and just shook it and turned it upside down, and it's all chaotic and things are flying all over and there's new information and there's mixed information and people don't know what to do," he added.

Former Vice President Joe Biden -- as he racked up more primary victories in Arizona, Illinois and Florida in the Democratic presidential race Tuesday -- focused on the coronavirus outbreak.

"You know, tackling this pandemic is a national emergency akin to fighting a war," he said.

"But it's also a moment where the choices and decisions we make as individuals are going to collectively impact on what happens."

Senate Minority Leader Chuck Schumer searched for historical analogies.

"Having lived through 9/11, having lived through the crisis in the banking system in 2008, I think people are more worried about the future and their own health, their own economic viability today than they were in either of those crises," the New York Democrat said.

Raimondo reached further back in history.

"What should be happening is we should be having a robust World War II-style federally driven mobilization," Raimondo said on CNN's "The Situation Room."