Christianity and Islam are both built on several concepts which they borrow from Judaism.
Christianity is an outgrowth of Judaism.
The premise of your question is wrong as many would classify 'Islam' as a major religion and it is primarily found in the Middle East, North Africa and parts of Asia. If you were to ask, 'Why were many of the major denominations of Christianity born in WE,' then that would get another answer.
Answer 1Israel is God's chosen people according to the Old Testament and will always have a part in His plan. When Christ came to Earth, Christianity sprang out of Judaism and they are closely related beliefs. The Old Testament is revered by Jews and Christians and the New Testament mostly by Christians.Answer 2Judaism is only really important (in a global scheme) because of the other religions that have grown out of it and the persecution it has received on a worldwide basis. Unlike the other major religions, it does not have the numbers to be a "major religion", but its worldwide impact does give it that importance. It should be noted that Judaism and Christianity are actually quite different religions and are not "closely related".
Among other differences, Judaism is monotheistic.
No, one is an Abrahamic religion (Judaism) and the other is an Indian faith.
Usually if you are of Hebrew descent, your religion is Judaism, but not always. There are approximately 500,000 Jews in the world who practice religions other than Judaism.
Judaism is a religion of one people, but accepts and welcomes proselytes from all other nations.
The major religion in Italy is Catholicism. In fact, Rome is home to the Vatican, which is the holy city for all Roman Catholics. Italy, however, does have other faiths. This includes Judaism, Protestantism, Hinduism, and even Islam.
Among other differences, Judaism is monotheistic.
Unlike other religions, Judaism is not centralised and there is no one leader.
The biggest difference between Judaism and other religions is that Judaism has few if any converts. If you are not born into the religion, then you are not part of that religion. Buddhism, Christianity, Islam, Sikhism, Jainism all welcome converts.
Judaism, :)