What, in your opinion, is the difference between the sin nature and being imputed with Adam's sin?
It's not my opinion.
The sin nature is the nature we're born with that tends toward sin.
This is the nature we have because there is none righteous, not even one. Romans 3:10
We are not born in a saved state and must become saved at some point.
Being imputed with sin means that each and every one of us IS RESPONSIBLE for Adam's sin.
God holds us as responsible as Adam was in eating the fruit.
This is incorrect. The bible teaches us that we are each responsible for our own sins, we are not responsible for our father's sins or anybody else - only our own.
2 Corinthians 5:10
For we must all appear before the judgment seat of Christ, so that each one may receive what is due for what he has done in the body, whether good or evil.
This is why a baby cannot go to hell as Calvinists believe.
The baby has not committed any personal sin.
He only has the sin nature.
Romans 8:5 NIV
Those who are dominated by the sinful nature think about sinful things,
This would be everyone, before salvation.
Adam (and Eve) sinned and disobeyed God's command not to eat from the tree of the knowledge of good and evil. Why did they disobey God? Because they were created with the sin nature, which has been inherited by all their descendants, i.e., all people (with one obvious exception!). Sin is imputed to all humans by Adam, righteousness is imputed to all believers by Jesus Christ. I'm not concerned with what "mainline churches" believe, only what the Bible says.
Adam and Eve were not created with the sin nature.
This would make God the creator of evil.
God cannot create evil because there is no darkness in Him.
1 John 1:5
This is the message we have heard from him and declare to you: God is light; in him there is no darkness at all.
Also, after God created everything in Genesis 1 and 2, He said IT WAS GOOD.
The sin nature is not good.
Genesis 1:31
God saw all He had created, and behold it was good.
Romans 5:13-15, "for before the law was given, sin was in the world, but there is no accounting for sin when there is no law. Yet death reigned from Adam until Moses even over those who did not sin in the same way that Adam (who is a type of the coming one) transgressed. But the gracious gift is not like the transgression. For if the many died through the transgression of the one man, how much more did the grace of God and the gift by the grace of the one man Jesus Christ multiply to the many!"
This is a different topic and won't get into it unless you really want to discuss it.
Again, sin is imputed to all humans by Adam, righteousness is imputed to all believers by Jesus Christ.
Christ's righteousness is imputed to us. Correct.
Adam's sin IS NOT imputed to us.
He cause the fall, but we are not PERSONALLY RESPONSIBLE for it.
Secondly, all children sin. With one obvious exception, there hasn't been a single child who hasn't told a lie, been disobedient to parents and/or teachers, etc. Every child has sinned and every child has been punished by their parents. Why? Because they have inherited the sin nature from Adam. If any person has inherited Adam's sin nature then they have no need of a Savior. Jesus died to pay the penalty for everyone's sins. There is no such thing as a totally innocent person.
Of course we all have inherited the sin nature.
Even babies.
BUT they're not responsible for any personal sin....
they've never sinned personally.
Ezekiel 18:20
20The soul who sins shall die. The son shall not suffer for the iniquity of the father, nor the father suffer for the iniquity of the son. The righteousness of the righteous shall be upon himself, and the wickedness of the wicked shall be upon himself.