According to the way the civil defense/disaster response system was set up after WWII, the federal government stockpiles, plans, coordinates and funds these responses. These systems have been set up for many, many years and are updated on a regular basis.
The federal government does assist states, who are expected to keep their own public health infrastructure in good shape. A significant part of every state's public health system is funded with federal money through the CDC and other federal agencies. It's also coordinated with DOD and the US military and all US health care providers are part of the system.
Truman and Eisenhower administrations helped set up our modern system. States do not print their own currency, so cannot accumulate debt. For this and other reasons, they're incapable of managing a pandemic on their own. It's too costly Why would we want them to anyway? Better to have a comprehensive, uniform, well coordinated response where everyone develops a response plan in their area, overseen, funded and guided by experts at the federal level.
http://www.centerforhealthsecurity....s/Clade-X-federal-pandemic-response-plans.pdf
https://www.fema.gov/pdf/about/org/ncp/pandemic_influenza.pdf