There are different schools of thought concerning the extent to which sin has affected us. Without a doubt, sin brings death (Rom. 6:23). Death is not a natural part of God's creation. When sin entered the world, death came with it (Rom. 5:12). But, to what extent and how deeply are we affected by sin? The Reformed theologians hold to the doctrine of total depravity. This is the teaching that sin has affected all of what the person is in body, soul, emotions, mind, and spirit. Furthermore, the Reformed position states that the effect of sin on our persons makes unbelievers incapable of choosing God on their own since sin has left us dead, blind (Eph. 2:3), and incapable of understanding spiritual things (1 Cor. 2:14).
In contrast, the Arminian position states that sin has affected all of what we are, but that it has not incapacitated the free-will choices of the unbeliever. The Arminian position states that the unbeliever is still capable of choosing or rejecting God on his own -- all he needs is some prompting from the Holy Spirit.
Nevertheless, the extent of the effect of sin upon us will continue to be debated by Christian theologians since the Scripture does not explicitly declare its depth.
Sin has also affected us by its influence on the world. All we need to do is look around us to see that we grow old, get sick, and die. In other words, the world is decaying and we first notice it in our own bodies. We also see the effect of sin on societies that war against each other. There is mayhem, killing, theft, adulteries, murders, lying, etc. Our jails are filled with those who are ruled by sin -- which is rebellion against God's truth.
Also, sin has affected the world in that there are floods, earthquakes, storms, etc. These are the result of an imperfect world with sin running through it. When Adam fell, the world was affected by his fall. Adam represented all of the created order since he was given dominion over it by God. Therefore, when Adam rebelled he took the world with him in his fall and as the Scripture says, it awaits its own deliverance:
"For the creation was subjected to futility, not of its own will, but because of Him who subjected it, in hope 21 that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God. 22 For we know that the whole creation groans and suffers the pains of childbirth together until now," (Rom. 8:20-22).
Sin will be remedied finally only by the return of Christ who will then destroy sin and death completely. Until that day, we war against the sinfulness of our fleshly bodies as well as the effects of it upon creation.