For a time, it looked as if his views would become normative in the Catholic Church. But towards the end of his life, A ugustine attacked Pelagianism, and eventually it was officially decreed heretical. The human will remains free to turn to God, and to do what is right. No one could be guilty of another person's sin. Infants could not be guilty of any sin.
Sin is transmitted from one generation to another but only by teaching and example.
Physical death is the natural end of life not a punishment for sin. Augustine thought that Pelagianism entailed that we could save ourselves by our own right choices and good works. He thought this was a terrible mistake, insisting that salvation is determined entirely by God. God's freely given grace is both necessary and sufficient for salvation. The answer is very little.