For me 'God' is a loose term. An advanced race of Aliens would appear to be relatively God-like, just like the first Conquistadors riding on horse back reportedly did to the Native Americans. I guess its how people personally define Atheism, obviously by your take one is atheist by default if not religious.
I for eg am not religious and do not participate in any religious activities however I hardly think of myself as a an Atheist because I associate being an atheist with the 'belief' or faith that a higher power does not exist. I dont believe I have the confidence in any such assertions, just our limited visibility and perception of 'reality', the notion of the forces mentioned represent very good reasons for remaining open minded on the probabilities and possibilities of the unknown