well…it didn't "open the door". Jesus had always come to save us all. that being said….
“Do not be arrogant toward the branches. If you are, remember it is not you who support the root, but the root that supports you” (Romans 11:18)
Jesus is the Root in case you think its you or any other human group. No matter the nationality…if your foundation is Jesus…if you are rooted in Jesus then you are Christian. Branches broken off are the natural Jews who rejected Jesus. Gentiles who have chosen to believe have been grafted in becoming part of the tree. But no branch is better than another.