Where are free spaying/neutering clinics in the United States?

Local vets, and the humane society would know. Kind of hard to give a general answer. Every city/town is different.

Some have low-cost clinics, but I've never heard of one being entirely free. Someone has to pick up the bill.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.