The Kingdom of Christ does not neutralize the things that make us unique. Paul's decree that there is no Gentile or Jew, circumcised or uncircumcised, etc., does not mean a loss of cultural identity. It means that all of those things are caught up in Christ, and that everything is reframed in light of that. This is the same Paul who says he is "all things to all people," so he definitely doesn't think we need to all look alike!