As an Australian living in Australia..
I was at a wildlife sanctuary in Tasmania, about 50 minutes drive from where I live.
The tour guide said something like: every year 250,000 native animals are killed every year on Tasmanian roads.
And I just blurted out: and they just keep coming.
Because, obviously, if it was a problem then that number wouldn’t be sustained. It’s kind of self evident that the deceased animals free up resources and territory for the living animals, who then go on to have more offspring.
I feel the same about cats: if they were a problem for the native fauna, we’d expect that problem to have auto-resolved by now, as in the cats would have killed all the native fauna.
But, like all environmental problems, it’s perennial: the problem always needs more funding, more restrictions on human activity, increased red tape for developers, and home owners who want to manage their land. Like you can cut a tree down until after it falls on your house and kills your infant.
Again, I don’t believe it’s well fed house cats that are allowed outside that are the problem, it’s the ferals that need to kill to survive.
And there are ways to solve that problem, or at least greatly curtail it.