There actually is a difference between Israel and the church.
And yet Paul says they are one new man in Christ, both comprising the body, of which He is the head. He is not the head of two distinct bodies, but one.
That’s why we have an Old Testament and a New Testament.
And this is what irks me about dispensationalism. You guys fracture the book into two separate entities, when it is one continuous book. The foundation of the NT scriptures is the OT scriptures. Without the OT, we have no NT. And lets say you are right for argument's sake. Your argument leads to this, the NT is not for the Jews today. If the OT is not for us today, then the NT is not for the Jews today. Are you willing to go that far with your belief?