The main reason is the feckless, incompetent pant-load sitting in the White House who abrogates his responsibility to orchestrate a unified federal response to an unprecedented national crisis. He's in stark contrast to several governors stepping into the breach.
If the Trump Administration had started barking orders at Governors (particularly to shut down business while if was still uncertain what havoc this virus could cause), the Governors would have immediately shouted for STATES' RIGHTS.The US Constitution (supposedly) only gives the Federal Government very limited rights. Nearly everything is left to the States. (IMO the Feds illegally overstepped their rights in refusing the Confederate States the right to secede from the Union by declaring war on the Confederate States.)
Most Americans have the opinion (and rightly so) that anything into which the Federal Government "sticks its nose" will be effed-up. America is too large and diversified for a "one-fits-all" policy on most things. Policies that work in California and New York do not usually work the same in Nebraska and Wyoming, etc. This is the same policy that governs US public school districts -- the idea that LOCAL government can better manage it than even State, and certainly more so that Federal governments.
But now that the incompetency and lack of preparation by several States is clearly evident, their Governors are shouting that the Feds should have covered their backs. You'll note that 9 States still refuse to implement "Stay at Home" orders. They aren't complaining about the limited Federal response.
And so it goes in the USA.