I happen to know Augustine and I happen to know the history of infant baptism.
I agree with QotQuesions...which happens to be a reformed site but it doesn't mean they're always wrong.
I DO NOT agree with Ency Brittanica.
This is an incorrect definition of OS as understood by mainline Christianity.
And you're correct.
And neither does the Catholic Church believe OS is a PERSONAL SIN.
Here are paragraphs 404 and 405 from the Catechism of the Catholic Church:
III. ORIGINAL SIN ⇡
The consequences of Adam's sin for humanity ⇡
404
How did the sin of Adam become the sin of all his descendants? The whole human race is in Adam "as one body of one man".293 By this "unity of the human race" all men are implicated in Adam's sin, as all are implicated in Christ's justice. Still, the transmission of original sin is a mystery that we cannot fully understand. But we do know by Revelation that Adam had received original holiness and justice not for himself alone, but for all human nature. By yielding to the tempter, Adam and Eve committed a personal sin, but this sin affected the human nature that they would then transmit in a fallen state.294 It is a sin which will be transmitted by propagation to all mankind, that is, by the transmission of a human nature deprived of original holiness and justice. And that is why original sin is called "sin" only in an analogical sense: it is a sin "contracted" and not "committed" — a state and not an act.
405
Although it is proper to each individual, original sin does not have the character of a personal fault in any of Adam's descendants. It is a deprivation of original holiness and justice, but human nature has not been totally corrupted: it is wounded in the natural powers proper to it, subject to ignorance, suffering and the dominion of death, and inclined to sin — an inclination to evil that is called concupiscence". Baptism, by imparting the life of Christ's grace, erases original sin and turns a man back towards God, but the consequences for nature, weakened and inclined to evil, persist in man and summon him to spiritual battle.
As you can see, the CC does not teach that babies are born with a personal sin.
However, you have correctly identified a problem:
In the 5th century Augustine DID change the reason for infant baptism.
Won't get into why the early church baptized infants...but Augustine changed
OS from meaning THE STAIN OF ADAM'S SIN to....
AN IMPUTED SIN.
This is not biblical, as many of Augustine's teachings were not...
and not even the CC, which you have mentioned, believes that it is.
Man is born TAINTED.
If you don't believe so, I hope you'll explain WHY man sins...I believe I've already asked this.
It is NOT an attack against God if Adam chose to obey satan instead of God.
It's an attack against Adam's descendants as he was the official rep of the human race.
Correct.
They are born innocent and remain so until the age of accountability.
But they are stained with a nature that is no longer in the proper relationship with God as Adam had.
Let's make it clear: If a baby dies...he goes to heaven.
Again, this is correct.
As I've stated before...I believe you have a problem with THE SIN NATURE.
I think I stated that even nature is awaiting redemption because when Adam sinned even nature suffered and
Adam became estranged from God, Himself, other humans and nature.
The sin nature affects everything.
Romans 8:19-22
19 For the anxious longing of the creation waits eagerly for the revealing of the sons of God.
20 For the creation was subjected to futility, not willingly, but because of Him who subjected it, in hope
21 that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God.
22 For we know that the whole creation groans and suffers the pains of childbirth together * until now.
The above will get into a different topic and it would be nice to stick to Original Sin for now.