They'd buy 1 or 2 fewer chickens per year. I don't think it'd register. You vastly underestimate the Big Ag chicken infrastructure. E.g. when McD's started serving chicken McNuggets years ago, they contracted for Every Chicken In Canada to supply the demand. Currently Americans eat 8 billion chickens a year, not to even mention egg factories. A million chickens from back yards is literally 'chicken feed'.
LOL, maybe so. But some of the homesteading videos on Youtube show people receiving shipments of anywhere from 30 to 120 chicks, which they raise as meat chickens, then after 8 weeks they slaughter them and freeze them. That's a lot of meat. Probably not for everyone. But imagine going through about 15 chickens a year, out of your own freezer, totally separated from the industry except for a breeder.
Then there's the freezer. Opting out of the (very efficient) chicken distribution system and choosing your own less-efficient freezer from whatever power grid, is arguably not going to be a smaller carbon footprint or whatever.
Its hard to beat big Ag for efficiency - that's cash-money to them and they've been at it for a century. Cottage industry agriculture is generally orders of magnitude less efficient.
