If its not a faith/belief that God doesn't exist, then it must be a fact claim that God doesn't exist.
If the latter, then its a positive assertion with an obligatory burden of proof/evidence.
If the former, then its just another theistic position.
Is it a faith claim that fairies, Santa, elves, gargoyles, etc. don't exist? If not, then why should a lack of belief in gods be a faith claim? You don't need to have faith to not believe or stop believing in something that has no observable evidence. You need "faith" to believe in something simply because you have been told to believe it, or it makes you feel emotionally secure to believe it, or you think you've heard voices telling you to believe it. One doesn't need faith to be an atheist. One simply loses or never had faith in the invisible entity that theists seem to think is real.
Have you ever known or cared for someone who was seriously mentally ill? I have many times during my long nursing career. My favorite mentally ill patient was a woman who honestly believed she was a queen. She honestly believed that she had been married many times, including once to Elivs. She honestly believed that she was ultra wealthy and had what she called a "castle palace" in New York City. She honestly believed that she was 35 years old, although she was actually in her late 70s. She was also dirt poor and her actual husband had died when she was in her late 50s. Apparently, she needed her delusions to be happy, and happy she was, as long as we didn't try to convince her that she was delusional. I don't think you are mentally ill, but there is something in your neurons that allows you to accept things without physical evidence. That's what faith is about. Just because we don't understand everything about the universe or if there is any meaning to our lives, doesn't mean that god exists and it has a plan for us.
I'm not claiming that one must be mentally ill to believe that a god has spoken to them or that there are invisible entities, angels, a demon etc. that really exist in some supernatural element. But, those are still delusions that our brains have created. Some people apparently need them in order to be happy or feel as if they are righteous. So, I get why the queen needed her delusions and I somewhat understand why theists need and then have no problem with having faith in things unproven and unseen.
Being a skeptic or being unable to believe in such things, doesn't take any faith or any delusions. Believing that I'm not a queen who has been married to Elvis don't take any faith. My brain isn't perfect, but it's functioning better than the brain of my dear delusional queen. Not believing in supernatural entities requires no faith.
I see that we're no longer making arguments for atheism, so I'm now just posting my opinion. Let's just say that after leaving my faith behind, I am no longer able to believe things that have no evidence and appear to be nonsensical to me.
If I ever become brain damaged or develop dementia, it's possible that I'll start imagining things are real despite having no evidence. But for now, I'm not capable of accepting that fairies, elves, demons or gods are real, outside of our amazing imaginations.