N = 1 but the cats I’ve seen around my neighborhood seem to be quite well cared for and simply killing for the sport of it, toying— ok, perhaps I’m anthropomorphizing— with their prey and often, IME not eating it at all

(in North America) and if we hadn't hunted and driven away the bobcats lynx and ocelots that would have killed those bird for food (along with the weasels stoats ferrets ermine mink foxes and other predators) how many birds would they have killed?

Generally speaking, if prey and predator evolve together then the prey have adapted and have a fair chance of escape/survival.

Non-native introductions usually have the issue of such a sudden population explosion that the prey cannot adjust in a timely fashion and get killed very quickly, very suddenly.

Fortunately for the birds then wild cats such as lynx bobcat and ocelot close cousin species to house cats were among those species we removed from the ecosystem before we introduced Felix catus.

We’ve introduced millions of cats into areas that haven’t had cats at all, like the entirety of Oceania.

Sure and that was bad. However using New Zealand as an excuse for pearl clutching in North America over cats, when there were several species wild cat here already not to (mention many other predators) that we decimated the populations of is disingenuous at best.