@skania,
There may be similarities that can be expressed far up the ideological pyramid, but here on the ground, the differences can be noted.
The primary difference as I see it is that Atheism makes no fundamental claim to Truth with a capital T. There may be individuals who do so, but the term atheism does not have inherent in it the idea that something is necessarily true.
This is not true of our major religions. Inherent in their ideology is the necessary truth of their dogma.
And ironically enough, though one need not appeal to science to be atheist, they often go together. And it IS inherent in scientific ideology/methodology that there is no Truth with a capital T. Despite the expression of recalcitrant scientists who may cling to their own dogmas, the definition of science lays at opposites and says there is truth until something else is discovered that replaces it.
If I may reify science (I know, a sin to myself!) it admits to its fallibility. Admits that we cannot know everything and are always learning, correcting, getting better knowledge - maybe..(because there are limits! So one never knows when one has reached them - gotta keep trying though!)
But science ain't no punk! You have to come with it if you want to overturn or propose something new. It does not suffer fools..and this, in my opinion, is the primary reason why religious people get rebuffed. Many of them twist, distort, abuse and otherwise do not understand scientific findings.
Like when the bible says that God stopped the sun from moving across the sky. Clearly the person who wrote that DID not think that his God stopped the earth from rotating. Clearly the people of that time did not take that to be poetic license. God really stopped the sun from moving. Yet now Christians assign that to the poetry bin because it MUST be obvious that its poetry because clearly the bible CANNOT be wrong. But people did not think this way for thousands of years. But that's not important to them. What's important is that Jesus died for our sins..fah!
Again, note the difference. Atheistic Individuals may express that they know the Truth, but that is an individual idea, not inherent in their atheism. Whereas with religion, it is inherent that their religion is inerrant.
If you want to go higher on the ideological chain, I have no qualms with you. But going up higher doesn't help us in sifting through what we actually talk about here, on the ground.