Christianity and Judaism are the same religion with a couple of changed rules, and an update on the supposed way to go to heaven.
Actually, there is a very big difference between the two religions. True Christianity is about salvation by faith alone. That's stressed repeatedly in the Bible, especially the New Testament. Judaism is based on salvation through physical, human works of redemption. Sure, we both believe in one sole God, but the similarities stop right about there.
Christianity has nothing to do with church attendance, priests, crusades, worship of the saints, or any of those other physical institutions. Like many people, you have confused Christianity with Roman Catholicism, which in my opinion is a complete heresy. The Roman Catholic church has performed hundreds of atrocities (like the ones you mentioned) in the name of God. They kept the Bible locked up for hundreds of years through the middle ages, and led people on wild goose chases for redemption.
True Christianity has nothing to do with that. The Christianity I follow is known as Protestantism, which you can see here:
http://en.wikipedia.org/wiki/ProtestantismAbout circumcision: circumcision is a law of Judaism, but is not a part of Christianity. Some christian parents do it as a symbol of their family's beliefs, but it is not required by God.
Finally, about Jericho: God was not wrong for having the people there slaughtered. Man is wholly God's, and He has the right to build up, and to destroy. God is not on the same level of being that man is, and He does not "owe" us anything, not even life. Nonetheless, He is a God who loves man and is not quick to anger.
