I'm always surprised when I see how far Catholics have come from their own faith.
The sin of Adam corrupted all men's nature. It is very much a "thing" -- it is a rebuttal of the truth, an obstinate will, a hateful longing for self and not God.
(For until the law sin was in the world: but sin is not imputed when there is no law. Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression, who is the figure of him that was to come. But not as the offence, so also is the free gift. For if through the offence of one many be dead, much more the grace of God, and the gift by grace, which is by one man, Jesus Christ, hath abounded unto many. And not as it was by one that sinned, so is the gift: for the judgment was by one to condemnation, but the free gift is of many offences unto justification. For if by one man's offence death reigned by one; much more they which receive abundance of grace and of the gift of righteousness shall reign in life by one, Jesus Christ.) Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life. For as by one man's disobedience many were made sinners, so by the obedience of one shall many be made righteous." -- Romans 5:12-19"Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned:
The sin of Adam corrupted all men's nature. It is very much a "thing"
You can call Adam's sin a thing if you wish.
You don't inherit Adam's sin, you "inherit" the consequences of Adam's sin. Specifically, your parents are unable to communicate to you sanctifying grace -- the indwelling life of the Blessed Trinity -- through the natural generation process.
Had Adam not sinned, they would have been able to do that.
There are other things that you inherit, but most of them are absences of things you should have inherited. Death is the absence of immortality. Concupiscence (tendency to sin) is the absence of the wisdom and strength of will to properly resist and understand sin. And so on.
Adam didn't "give" you anything. He squandered your inheritance. If your great-grandfather squanders your inheritance, does your father transmit poverty to you?