Well, see, that's the whole point! I don't believe in any church founded by man, I believe in Jesus Christ and it is this faith that places me within His universal body/assembly/church. You talk as if the "Church" is some kind of ethereal organization that has power and authority yet you don't seem to comprehend that the church is PEOPLE, believers in fellowship with other believers throughout the world from all times, places, nations and tongues. It is the faith of Jesus Christ which binds us to one another - that spiritual house - no matter what the sign might say on the door to our meeting place.
The commission to preach the gospel began with Jesus sending out His disciples and followers and they in turn sent out those they led to saving faith. Local assemblies were established and pastors, teachers, elders, deacons, etc. were set up to manage the household of God, the church of the living God, which is the buttress/support and foundation of the truth. This same commission exists today and our duties as servants of the Lord remain the same. Our guidebook is Holy Scripture, our rule of faith, given to us by God so that we are complete, fully equipped unto every good work for His glory. It IS one fold, one flock. Don't limit the work of the Holy Spirit to accomplish this.
Your comment: “Well, see, that’s the whole point! I don’t believe in any church founded by man, I believe in Jesus Christ and it is this faith that places me within His universal body/assembly/church.”
Well then, it sounds like that you maybe a member of the Body of Christ - His Catholic Church which Jesus founded for our salvation.
Since his Ascension and until the end of history, Jesus lives on earth in his supernatural body, the body of his members, his mystical body. Having used his physical body to redeem the world, Christ now uses his mystical body to dispense “the divine fruits of the Redemption” (Mystici Corporis 31).
The Church: His Body
What is this mystical body? The true Church of Jesus Christ, not some invisible reality composed of true believers, as the Reformers insisted. In the first public proclamation of the gospel by Peter at Pentecost, he did not invite his listeners to simply align themselves spiritually with other true believers. He summoned them into a society, the Church, which Christ had established. Only by answering that call could they be rescued from the “crooked generation” (Acts 2:40) to which they belonged and be saved.
Paul, at the time of his conversion, had never seen Jesus. Yet recall how Jesus identified himself with his Church when he spoke to Paul on the road to Damascus: “Why do you persecute me?” (Acts 9:4, emphasis added) and “I am Jesus, whom you are persecuting” (Acts 9:5). Years later, writing to Timothy, Paul ruefully admitted that he had persecuted Jesus by persecuting his Church. He expressed gratitude for Christ appointing him an apostle, “though I formerly blasphemed and persecuted and insulted him” (1 Tim. 1:13).
The Second Vatican Council says that the hierarchical structure of the Catholic Church and the mystical body of Christ “form one complex reality that comes together from a human and a divine element” (Lumen Gentium 8). The Church is “the fullness of him [Christ] who fills all in all” (Eph. 1:23). Now that Jesus has accomplished objective redemption, the “plan of mystery hidden for ages in God” is “that through the Church the manifold wisdom of God might now be made known to the principalities and powers in the heavenly places” (Eph. 3:9–10).
According to John Paul II, in order to properly understand the Church’s teaching about its role in Christ’s scheme of salvation, two truths must be held together: “the real possibility of salvation in Christ for all humanity” and “the necessity of the Church for salvation” (Redemptoris Missio 18). John Paul taught us that the Church is “the seed, sign, and instrument” of God’s kingdom and referred several times to Vatican II’s designation of the Catholic Church as the “universal sacrament of salvation”:
“The Church is the sacrament of salvation for all humankind, and her activity is not limited only to those who accept her message” (RM 20).
“Christ won the Church for himself at the price of his own blood and made the Church his co-worker in the salvation of the world. . . . He carries out his mission through her” (RM 9).
In an address to the plenary assembly of the Congregation for the Doctrine of the Faith (January 28, 2000), John Paul stated, “The Lord Jesus . . . established his Church as a saving reality: as his body, through which he himself accomplishes salvation in history.” He then quoted Vatican II’s teaching that the Church is necessary for salvation.
In 2000 the CDF issued Dominus Iesus, a response to widespread attempts to dilute the Church’s teaching about our Lord and about itself. The English subtitle is itself significant: “On the Unicity and Salvific Universality of Jesus Christ and the Church.” It simply means that Jesus Christ and his Church are indivisible. He is universal Savior who always works through his Church:
The only Savior . . . constituted the Church as a salvific mystery: He himself is in the Church and the Church is in him. . . . Therefore, the fullness of Christ’s salvific mystery belongs also to the Church, inseparably united to her Lord (DI 18).
Indeed, Christ and the Church “constitute a single ‘whole Christ’” (DI 16). In Christ, God has made known his will that “the Church founded by him be the instrument for the salvation of all humanity” (DI 22). The Catholic Church, therefore, “has, in God’s plan, an indispensable relationship with the salvation of every human being” (DI 20).
The key elements of revelation that together undergird extra ecclesiam, nulla salus are these: (1) Jesus Christ is the universal Savior. (2) He has constituted his Church as his mystical body on earth through which he dispenses salvation to the world. (3) He always works through it—though in countless instances outside its visible boundaries. Recall John Paul’s words about the Church quoted above: “Her activity is not limited only to those who accept its message.”
https://www.catholic.com/magazine/print-edition/no-salvation-outside-the-church
Catholics believe that as Jesus Christ lived his natural life on earth two thousand years ago in a body drawn from Mary, so he lives his mystical life today in a body, drawn from the human race in general, called the Catholic Church. Catholics believe that her words are his, her actions his, her life his (with certain restrictions and exceptions), as surely as were the words, actions, and life recorded in the gospels. It is for this reason that they give to the Church the assent of their faith, believing that in doing so they are rendering it to God himself. She is not merely his representative on earth, not merely even his bride: In a real sense she is himself. Catholics believe that in this manner, as well as in another that is not our business at present, he fulfills his promise to be with his disciples all the days, even to the consummation of the world.
“I am the vine, you the branches,” or, “He that heareth you, heareth me: he that despiseth you, despiseth me,” or, “As my Father sent me, even so send I you.”
For the only distinction possible to draw between the Vine and the branches lies in saying that the Vine stands for the whole and the branches for its parts. The branches are not an imitation of the Vine, or representatives of the Vine; they are not merely attached to it, as candles to a Christmas tree; they are its expression, its result, and sharers of its life. The two are in the most direct sense identical. The Vine gives unity to the branches; the branches give expression and effectiveness to the energy of the Vine; they are nothing without it; it remains merely a divine idea without them. You cannot, that is, apprehend the Vine at all in any real sense as vine except through the branches. So, again, in passage after passage of Paul’s writings, phrases are used that are practically meaningless, or at the best wild and furious exaggerations, unless this identity of Christ and his Church is assumed to have been in the writer’s mind.
https://www.catholic.com/magazine/print-edition/christ-in-the-church