It made a dent in Leaf's food shortages, which IIRC is a town of ~10000 people. We'd need a lot more food to feed Fire Country as a whole, much less make a difference for the Elemental Nations in general. Distributing that food to thousands of tiny villages would be a huge logistical challenge.Dog territory houses bison (?) herds that have hundreds of thousands of bison in them. I think Cannai was willing to let us take enough meat to make a sizable dent in Leaf's food shortages a while back, while also saying that it's sustainable for them. I think there's quite a lot of food we can import if we really try, but we'd need a shit ton of storage seals to carry them all and ninja to oversee logistics.
Also, I think the Elemental Nations are basically stuck in the malthusian trap, and importing more food will after a decade or two probably result in a larger number of people living the same near-starvation lives (and maybe also a new class of people living comfortably by siphoning off food imports, because we cannot possibly avoid corruption if we do this at scale). And then if any of those trade deals fall through, or we loose a summoning scroll, there's a sudden food shortage and thousands of people starve.
So plausibly we could cause more people to not starve in the short term, and a larger population in the long term, if we spend some large quantity of resources to import food and accept a more fragile food supply. Which might be worth it, but I don't think it comes anywhere close to actually solving the problem in any meaningful way.