I said to the poster, in so many words, there is one Lord (i.e., King), one nation, one Kingdom; the Kingdom of God the Catholic Church. Those claiming to be "Church" are not "church" in the same sense as the One Body of Jesus Christ. You should ask yourself how can such claims be valid, as God's truth, thus absolute. A Church, any Church is the body of Christ.
Let's address what the "Church" is not. Today it is the trend to say the unique differences between the various Christian religions are deemed inconsequential. This however is “based on incorrect theological perspectives and is characterized by a religious relativism which leads to the belief that ‘one religion is as good as another’ (Pope John Paul II, Redemptoris mission, December 7, 1990). I've found that the Church of Jesus Christ cannot participate in a definition of 'one is as good as another. Divine Truth is not an amalgamation of partial Divine Truths. Since faith resides in the intellect, this type "just-as-good-as" faith is "one's own invention and milieu" and will not "bring us into the company of believers", i.e. the Catholic Church. This one size-fits-all perspectives leads to a dead faith. (Cf. Pope Benedict XVI, Principles of Catholic Theology: building stones for a fundamental theology, 1987) Thus, the Church is not a company of like minded believers joined together by some vague vibe of Christ's Divinity and Christ's humanity. God's word is immutable, never changing, and incorruptible; thus we find "God is Truth" (Cf. St. Thomas Aquinas). There is only one True Word of Christ that resides in only one teaching authority, the Catholic Church. Any other is false. Only a Divine College can infallibly teach the disciplines of an irreformable Truth. Only the Divine can receive and bind others to immutable Truth with an authority to obliges the faithful. This Divinity resides only in the Catholic Church under one head, the Roman Catholic Pontiff.
The Church is constituted for the salvation of the faithful; explicit in the doors opened in baptism she is necessary for redemption. She is a corporate family of adopted ‘sons of God’ redeemed through God's merciful graces given without consideration of due merit or demerit. "He that believeth and is baptized shall be saved: he that believeth not shall be condemned" (Mark 16:16). The Church is the Divine Motherhood of our salvation; consequently we find our devotion to the Blessed Virgin as the personification of the Church is a gift from heaven. Nevertheless, the Church is simplistically defined as the "Body of Christ". The totality of sacramental life is found in Sacramental Body of Christ.
"If Christ is the sacrament of God, the Church is for us the sacrament of Christ; she represents him, in the full and ancient meaning of the term; she makes His reality present. She not only carries on his work but she is his very continuation, in a sense far more real than that in which it can be said that any human institution is its founder's continuation." (Henri de Lubac, Catholicism: Christ and the common destiny of man, English edition 1988 , French original, 1947, p 76)
JoeT