I am always amazed that so much emphasis is directed at the first part of those verses, and so little emphasis is given to understanding what has been said in the second part of those verses and what it all means.
Who is doing that? It happens to be the particular
part of the scripture that is being addressed.
I will just say here that the real message there is the comparison between the effect of Adam's disobedience and the effect of Jesus' obedience. The really strange thing is that so many see the effect of Adam's disobedience to universal while the effect of Jesus' obedience to be severely limited; in other words, Adam's work is much, much more efficacious than that of Jesus. For me that is simply unacceptable and wrong. In verse 18, for example the meaning of all men in the second part is not different from the meaning of all men in the first part.
I am not missing the message of the scripture in total. We are
discussing the effect Adam's sin had on all humanity as per your claim that Adam's sin is not imputed to humanity, and that because of Adam's sin we have a nature to sin, whereas we were created without a nature to sin, but an ability to do so.
The Bible shows that the effect of Adam's disobedience is universal. It also says so directly. "All have sinned and
fall short of the glory of God." It shows and tell us that Christ's righteousness (obedience) is universal in that it includes the whole world, Jew and Gentile, but it is not universal in the same way as Adam's sin was. It does not include unbelievers, so it does not include every man, woman, and child. The They remain in Adam. The meaning of "all men" in the first part is every man, the natural condition of humanity. The meaning of "all men" in the second apart means all types of people all over the world. The Bible shows and tells us this. Empirical evidence shows us that. Not all men are saved. Only those in Christ through faith. "By grace you are saved through faith."
Many would agree with you, but that simply cannot be true. The physical death of mankind, or anything else for that matter, did not result from Adam's sin. In fact, the physical death of Adam didn't result from his sin. Adam died because God ejected him from the Garden taking away his access to the fruit of the tree of life which was there to stave off his physical death (Genesis 3:22)..
And exactly why did He eject him from the garden? First cause. Second cause.
"Through Adam death came to all men." Paul was speaking of physical death, which includes what is called spiritual death.
That there is an imputation of Adam's sin to all mankind does not mean that God is punishing us for Adam's sin. The punishment we receive and which Jesus took in our place, because they were imputed to Him, is for our sins. They can now not condemn us. He also defeated the power of Adam's sin imputed to us and the power of death to hold us.
Adam's sin imputed to us simply means that Adam as our federal head (the representative for all men) resulted in mankind as a species being condemned---fallen from the glory of God in which we were created. We became as a species, sinners.
The third form is the spiritual death that is the condition of the spirit of a physically alive man separated from God. This third form is the result of our sin in our life, as was Adam's (spiritual) death on the "day that he disobeyed God's command to not eat of the fruit of the tree of knowledge of good and evil.
All mankind suffers from this spiritual death, not
just because of or when we commit our own sins. It is a result of what Adam did and it is why we cannot make ourselves spiritually alive. We cannot change who we are as a species in relation to a holy God. And because we are in this condition the Bible tells us we cannot even understand or desire spiritual things. That is, those things that pertain to life and holiness and our need for God. 1 Cor 2:14 But the natural man receiveth not the things of the Spirit of God, for they are foolishness unto him; neither can he know them because they are spiritually discerned.
Which completely destroys the concept of free will choice for God. How can one who is spiritually dead even understand or desire, let alone believe, the spiritual things in the gospel. How can we do that if we are spiritually dead in our trespasses and sins? Unless we first be quickened to life, made spiritually alive? Can we raise ourselves from this condition of spiritually dead? Can we change the fact that we are born in Adam?
The place to look for that answer would be the scriptures. One of many come to mind immediately, and it says that God made us alive while we were in that condition, and He did it by making us alive with Christ, the resurrected Christ, and seated us with Christ and in Christ in the heavenly places. By grace, grace, grace, you have been saved, through faith that is a gift of God. A gift given, not offered. Eph 2:1-10.