If you look around any city, even, NYC, there is plenty of protein to be found among the critters that live there, if you are willing to consider them a fod source. Strangled rat is not my ideal meal, and I'd need to be real hungry to eat it. However, I like knowing it's there, available, in case.

Pigeon is something that I'd prefer over rat, and I think one might be able to capture pigeons and treat them as one might other domesticated birds. Maybe, you'd rather have pigeon eggs than no eggs.

Any of these would need to be for very long term scenarios. I don't see such events in the U.S.'s near future. It could be a choice for someone low on other resources, out of work, no money, etc., but as far as a resource for a community, I think food will be brought in within a week, nevermind the 3 weeks over which most of us can survive.

As far as a resource to store to ensure you have a pretty healthy diet, as in one that provides the minimum amount of protein, calories, vitamins and minerals, it is tough to beat things like Mainstay bars. They were designed to be a person's sole source of nutrition for a pretty long period of time, because they were desiigned to be the food you put in a ship's lifeboat.