I entirely agree, this would be great. I don't see why it has to be done in cities though. Farmers in smaller co-ops can provide a similar decentralisation.

Not all parts of US can be farmed

The grocery stores are low on stock because of selfish people panic buying, not because there's not enough food. The supply chain is still functioning normally.

The supply chain is functioning normally, but "normal" means ~40% of food consumption in urban areas occurs via restaurants. The supply chain isn't designed for 100% of folks buying groceries at the supermarket and preparing their own food.

And that's sort of the problem. The normal centralised supply chain optimises for normal usage patterns, and adapting to abnormal usage patterns causes widespread issues in the short term.

A decentralised supply chain is (at least in theory) better able to adapt to local distrubances.

How do you imagine a de-centralized supply system, with each urban area's cell optimized for 40% of produce going to restaurants, would respond differently?

You're absolutely right. De-centralized systems can definitely respond better to local disturbances. Conversely, they're sometimes more vulnerable to larger scale disturbances that can more easily overwhelm the capacity of smaller systems to absorb shocks.

The system looks pretty damn robust given that we've just shut the global economy down and the food still keeps coming in. Maybe with some hiccups but that's complaining at a high level.

The reason decentralization doesn't make a lot of sense is because we need to produce food cheap and at scale to feed the world. Putting thousands of dollars into vertical farming equipment that doesn't fit into the apartments of most people on the planet is kind of silly.

There's also simply division of labour at work here. It's uneconomical for large portions of the population to spend their time farming.

It's essentially just a recreational hobby for wealthy people or maybe reasonable on a Mars Colony, but here it does not make much sense.