A report from the Trust for America's Health, says the United States only has 965,256 staffed hospital beds, and in the event of a pandemic, half a million Americans could die and more than 2 million could end up in the hospital with serious complications.
This would happen if an even moderately severe strain of a pandemic flu occurs.
The state-by-state analysis, by the non-profit group, adds to growing demands that the United States needs to be better prepared for a large outbreak of disease, whether natural or brought on by war or terrorism.
The Trust's executive director, Shelley Hearne, said in a statement, that this is not a drill or a planning exercise.
Each year, influenza kills an estimated 36,000 Americans and puts 200,000 into hospital.
Every few years a more serious strain strikes and on average a so-called pandemic strain emerges once every 27 years.
The more virulent strains sweep around the world within months.
The world was hit by pandemics in 1918, killing up to 40 million people globally, and in 1957 and 1968.
Many health experts say the world is overdue for another and they fear the avian flu in Asia may be it.
The World Health Organization says an H5N1 avian flu pandemic could kill up to 7.4 million people globally, because people lack immunity to it.
As yet Avian flu has not acquired the ability to pass easily from person to person, but experts say it would spread rapidly if it does.
But according to the report another strain of flu with pandemic characteristics could also wreak havoc.
The report is very critical and says the U.S. has not adequately planned for the disruption a flu pandemic could cause to the economy, daily life, food and supply distributions, or homeland security, and lags behind both Great Britain and Canada based on an examination of leadership, vaccine development, vaccine and antiviral planning, health care system surge capacity planning, coordination between public and private sectors, and emergency communications planning.
Health officials say they are aware of the warnings and are developing a plan. The heads of the Centers for Disease Control and Prevention, National Institutes of Health and Health and Human Services Department are apparently regularly called to hearings before Congress on the issue.
The Trust says more could be done now in preparation, including setting up plans to track an outbreak, stockpile antiviral drugs and other medical supplies and set up communications.
The study says that the United States has stockpiled 2.3 million courses of the best anti-influenza drug, Tamiflu and has placed orders for 3 million more courses of the drug, which does not cure influenza but can prevent infection and can reduce its severity if taken early enough.