The claim about size is basically a red herring. A small independent nation could set whatever course it wanted. But California is administered on a day to day basis based on Local, State and Federal policy. You might see local and state officials and workers more often but to a substantial degree they are executing Federal policy that come in the form of grants to states and municipalities.

And this is to say that the states are not prepared act as nations at a moment's notice and without the expectation that they will act independently, they don't have either the resources or the experience (but I guess they're learning fast).

Even more, if you live in the US, you might have noticed you pay far income tax to the Federal Government than to your state government. A lot of this money goes back to the states but only for particular, mandated purposes. This makes it rather difficult, again, for states to suddenly offer their own emergency management system, especially when Feds have a fully budgeted emergency management agency (FEMA, the, uh, Federal Emergency Management Agency) where the states don't agencies with equivalent funding. So when FEMA doesn't actually act, we have a serious problem.