And even aside from the temptation to use the supplies, not everyone would be able to find a place to store a month of rations & water.
And that is expensive (something like $1k per household, perhaps, based on https://www.costco.com/chef's-banquet-one-month-emergency-fo... ).
The US is amazing at transportation in general, and it makes more sense for each state to maintain emergency supplies they can move in a moment's notice.
But households should in general be prepared to survive about a week without outside assistance; if you're more wealthy you can increase that.
Great planning work.
An emergency food stash that is part of a go-bag / bug-out-bag is useful. Individuals or households would have their food, clothing, and vital documents in a single piece of luggage (duffel bag, backpack, suitcase), which could be grabbed and carried or quickly thrown into a vehicle.
The challenge, at a wide-scale (national, regional, even city-wide) disaster-preparadness level, is of communicating this and establishing suitable levels of conformance.
To the extent that there are preparations which individuals can self-provide (food, water, and clothing among them) and those which require or benefit from central coordination (command-and-control, warning and information systems such as the FEMA test, emergency responders (rescue, etc.), and coordinated mass transportation (establishing and managing evacuation routes, busses, trains, etc.) it might not make sense to specifically provision such supplies, though if specific items aren't readily available commercially government coordination or distribution might help.