Ok: per google
Domestic cats: https://www.statista.com/statistics/198102/cats-in-the-united-states-since-2000/
Feral: https://en.wikipedia.org/wiki/Feral_cat#Distribution_and_habitat
From what I gathered in a few minutes on google, there are approximately 140 million domestic and feral cats in the USA. Even if every one of them lived outside all the time, there is still no way possible to kill that many birds. Sorry.
Fudged numbers.
Ignore it if you like but it’s indisputable that cats are major pests that kill even if they are well fed house cats. You can say that the numbers are fudged but even if you take off a few zeroes you end up with invasive killing machines.