I agree with your post here. Most definitely the domestic cats contribute to the problem of feral cats, however if all domestic cats were kept indoors there would still be the problem of feral cats. I'm pretty sure they would manage without the input of the domestic population! :-)
I'm afraid you're right. However a remarkable number of birds are killed by domestic cats which are allowed out, despite the fact those cats are regularly fed.
The bottom line is that few municipalities seem to be willing to spend the money required to control their feral animal populations. In some cities, like Los Angeles, wild dog packs are a real problem. If city hall can't do anything when people are attacked, I don't see that they'll do anything when it's just wild birds being killed.