If babies are born with souls of awaiting angels, then they most certainly are not atheists.
There is No ' if ' about 'born with souls' because in Scripture Adam did Not come equipped with a separate soul. Adam was a soul - Genesis 2:7
Adam did Not have a soul, Adam did Not possess a soul, rather Adam was a living soul. At death Adam became a dead soul or life-less soul ( person )
Angels were created before material creation and humans came into existence.
Adam was made from the dust of the ground, and ' returned ' to where Adam started - Genesis 3:19
So, at death Adam simply ' returned ' to the dust of the ground. A person can Not ' return ' to a place he never was before.
If people had an immortal soul then the soul could Not die, the soul would be death proof.
Death-proof souls do Not need a resurrection, but dead souls need a resurrection in order to live again.
According to Ezekiel 18:4; Ezekiel 18:20 and Acts of the Apostles 3:23 the soul that sins dies, and a soul can be destroyed.
So, souls are mortal and subject to death or even destruction - Psalms 92:7
Unless damaged, babies do come equipped with a built-in conscience, but ' faith ' (confidence) in God is learned by effort and God's blessing upon a person's effort.