Israel was full of doubt and unbelief, even as God was leading them to the promised land. The nation did not cease to be God's at any time. Israel was, is and will be God's nation until the new heavens and new earth come into being. If you have an issue with that, tell God, not me.
And this is the same as the church. As our journey as Christians in this world, we fail, we doubt, we are blessed, we are hated,
We have false prophets, false teachers, and as right now we too are waiting for our savior to return.
God has chosen israel to be a peculiar people. One has to admit the jews are by far different from all the rest of the world.
We are a new creation a new creature grafted into that peculiar people tree to bring forth a more excellent offering to God.