in response to Godslove 260,.... these are very good questions! comprehensive answers would take a book or two.
here are some humble ideas from me...
1. you say ...'We are taught that we do not inherit Adam's sin..'
Whoever teaches that deserves one brownie point because it causes you to raise these kind of questions but not necessarily because it is true!
2. you say... 'yet we do suffer the consequences of his sin, the loss of Grace...'
this second half of the statement suggests that 'to suffer the consequences of sin' is 'loss of Grace..' I think, they are not the same thing. In fact, sin stirs up both, God's Wrath (Romans 1:18) ands God's Grace (Romans 5.20). The difficulty is in that not all the sinners are subject to God's wrath, as some of the sinners are subject to His grace (Romans 9, vs.22-23...).
3. you asked... 'But WHY do we suffer the consequences of his sin?' ...
well, we cannot escape the reality of being born sinful.(Ps.51 vs.5 states: 'surely i was sinful at birth, sinful from the time my mother conceived me'). Being born sinful does not mean that a baby can commit any sin but it simply means being subject to the law of sin which is within us from conception.(see Romans 8) This is our spiritual heritage from our father, Adam. He rebelled against God, and we, like any child born into a family of rebels, inherit the status of 'spiritual rebel' from our father, Adam. we cannot choose to whom we are born, thus we cannot choose the status we inherit, nor can we reverse the status of 'spiritual rebel' by rebelling against this spiritual/natural law.
4. you asked... 'Why can't every human choose for themselves to separate themselves from God? Why are we bound by the decision Adam made?'
well.. imagine a world in which children would be able to choose their parents...!.. in such case we would think that every child would choose to be born into a royal family where is plenty of safety, riches, power, etc.. but we may well be wrong!! Adam was 'born' (made by or belonged to) to the King of the Universe(s). He new God personally. Adam had personal and direct access to the beauty and splendor of God.. every morning. And yet, he rebelled!!! Why then should we want to have that same choice individually?.. We wouldn't have done any better than Adam, anyway. And suppose we did... as in , some of us would not have rebelled. What's the advantage in this case?.. None! because we would not have known the beauty and the Glory of His Grace!! It takes a forgiven SINNER/REBEL to marvel at the Glory of His Grace. No rebellion..no Grace! Flipping the coin, why should somebody not want to marvel at the Glory of God's Grace??!!! Is this not some kind of rebellion?.. Refusing God's Grace is rebellion indeed. And if we do receive His Grace, why does it matter how we became sinful, whether through personal choice or heritage. ..?..
5. you said... 'If we claim that any human in Adam's place would have done the same, then we are saying that we were designed by God to fail..'
This is not only a logical conclusion, but it also seems to be a biblical one. Romans 9 spells it out for us all. I recommend you read it. Also, chapter 8 vs. 20 reads.. 'For the creation was subjected to frustration (futility) not by its own choice but by the will of the one who subjected it, in hope that the creation will be liberated from its bondage to decay ...'
i hope someone would find my summary helpful....