God sees the world as Israel and non-Israel (the fancy word is "gentiles"). God never asked Israel to stop being Jewish, and God never asked non-Israel to become Jewish (although he does ask both sides to believe what he says).
The "church" as the Bible says is "the body of Christ", and Israel is still Israel, because their story is not over. God's promises to Israel are still alive. The fact that Israel exists at all, becoming its own country again in 1948 after over 2000 years, is enough proof for me.
Calling the church the "body of Christ" sounds funny. I think it just means that people who believe in Jesus should try to be like him on earth until he returns. It's hard, um, well impossible to do without lots of humility and supernatural help.
"Believing" just means that Jesus Christ (called Y'shua Messiah in Israel) really was God in a man's body, who sacrificed himself for everyone.