In ordinary times, yes, the US is a federal system of states with some level of individual state rights. But state power has somewhat eroded over time; federal supremacy is a thing; and there is plenty of precedent for the Fed stepping in during emergencies and war. (And war is a relevant point of comparison because even if this thing goes as well as possible at this point, it's likely going to kill more Americans than any foreign war and probably more than the civil war.)

No, the reason the top level federal government isn't doing much is because Trump is an incompetent idiot who doesn't have a second brain cell to rub against the first. The federal government has the funds and the coordinating agencies (FEMA, CDC, military and national guard) and could be buying masks, ventilators, tests; solving distribution problems; coordinating with states on social distancing and even lockdown/shelter-in-place policy. They did nothing during the early weeks when they knew it was a coming problem and it is not clear how much Pence is doing now.