On a nationwide scale, yeah probably not, but nor do I think it should be done at the federal level. You could get economies of scale on purchasing and storage, but I suspect there would be more inefficiencies emergent from such a large scale thing than would be worth it. Each geographic area has very different needs, very different population makeups, and more, so somebody local is much better equipped to evaluate and plan. Even just "how much water to store" varies immensely. If you're on a water shed in an area with frequent rainfall, it would be wasteful to store a ton of water, but if you're in a desert water storage is one of the most important things. But even just communication setups like ham radio and designated response personnel is something that needs to be worked out locally.

I've been involved in several different cities emergency preparedness plans though, and there is actually a lot more happening in the US than most people think or know. It rarely if ever makes the news, but it happens.