Here in the UK we don't have this moral panic over outside cats. It seems to be a uniquely New World problem.
https://mobile.abc.net.au/news/2019-07-15/cats-kill-billions...
The most recent figures of how many creatures are killed by cats are from the Mammal Society. They estimate that cats in the UK catch up to 275 million prey items a year, of which 27 million are birds.
Joakal claimed billions. Your link says a quarter billion just in the UK.