If you kill feral cats, less feral cats can call wildlife.

How would that be carried out? Many states have programs to reduce nucence wildlife. Like wild hog control programs. Pennsylvania had dog wardens that round up stray dogs. People are also required to get dogs licensed (but not cats, unfortunately). Contractors are also contracted to do that.

I'm not afraid of cats, using names and insults are not making your argument valid. TNR doesn't reduce the problem.

The longevity would be ongoing. You can't just ignore the problem. It requires proper management until people don't let their cats outside.

And yes, feral cats have been eradicated in some places. Specifically on islands where they were decimating wildlife populations. The same has been done with rats.

I hope that answers your qlquestions and soothes whatever anger you have to use all those insults.