There is no country on Earth that is gonna lock up all its citizens indoors and starve them to death. Governments aren't that stupid.
And were there not videos of government agents welding bars on windows and destroying food to punish quarantine breakers recently?
I think you're dramatically oversimplifying how this all works.
First of all, you have to schedule a specific time slot to go shopping, to ensure that the store never gets too crowded. Secondly, you aren't allowed within two meters of anyone at any point. All of the store employees are wearing protective gear (gloves, masks, etc.). When you checkout, you push your cart up to them, they ring everything up, set it back down, and then you pack your bags yourself while they go away (to maintain a distance of two meters). They might be changing gloves with every checkout, too.
I have less knowledge of China, but I think it's similar. I saw a video of a ranged thermometer being used on every person before being allowed inside. Maybe Italy is doing similar. If and only if you have a fever or a confirmed infection then are you not allowed to leave your dwelling at all (unless it's to go to a hospital); that's when you get your food delivered.
With containment measures this drastic, you can definitely keep the infection rate below 1, which is all you need to stop an infection. And it's exactly these kinds of measures that need to be taken, because food is essential. You cannot have people starving to death en masse. Grocery stores are essential, and it's possible to allow grocery shipping while largely mitigating the spread of disease. Needless to say, all gatherings are banned, most stores are shut, and restaurants are to-go/delivery only (if they're even still open).
And I'm not drastically over-simplifying things, unless you somehow think that "shut down almost everything except for grocery stores and healthcare" is "over-simplified". This is working in China. They are stopping the spread of the disease while simultaneously maintaining access to food and healthcare.
The whole supply chain is guaranteed (and related companies allowed to work).
Source: I'm italian and directly affected by this
The food production aspect though is more problematic; it can involved larger groups of people and more human contact.
Economies aren't just playthings for little pieces of multicolored paper -- they're the process by which we live a life different from that of a wild animal.
Life without an economy would be smelly, brutal, and short.
Personally, I pray that the US won't try this idiocy, and further pray that people won't stand for it if they try.
At this point if you don't have at least a week's supply of rice on hand you're just being careless. It's dirt cheap and large sacks are readily available everywhere.
But in all seriousness, general guidelines are already that, even without stuff like Corona or not.
One advice from the supply chain perspective, so. If you have to stock up, do so in small quantities across multiple stores. reducing the number of stock-outs at the point-of-sale has an unbelievable efeect in stabilizing supply chains. and the last thing we want is unstable supply chains right now. As rediculous as it is, if something like th toilet paper scare happens to more life-ciritical stuff things turn a lot less funny rather quickly.