Something is a truth simply because you, as a "believer," feels it is such?
Have you forgotten that Christianity is not something God shoves down the throat of the unwilling but something He offers to the willing? We are not required to be saved - we are freely invited.
God gives us the grace to know the truth freely, if you are so inclined to accept it. He does not offer anything to the hard-hearted, those puffed up with pride who view the ultimate authority as residing within themselves. Christ purchased us with His blood and we are all called to believe the truth and to follow the doctrines He taught. He is our Supreme Legistlator as well as our Savior.
On what did the Catholic Church base it's authority during the intervening three centuries?
On the Divine Commission: "Going therefore, teach ye all nations; baptizing them in the name of the Father, and of the Son, and of the Holy Ghost. Teaching them to observe all things whatsoever I have commanded you: and behold I am with you all days, even to the consummation of the world." (St. Matthew xxviii.19-20) He established a Church to teach His Way so that the faithful wouldn't be lead astray by the erroneous doctrines of false prophets and wolves in sheep's clothing - which most Protestants fall headlong into, as the "truth" is merely a matter of their personal opinion.
"Write therefore the things which thou hast seen, and which are, and which must be done hereafter." (Apoc. i.19)
St. Paul was commanded by God to write to the seven bishops of Asia in Ephesus, Smyrna, Pergamus, Thyatira, Sardis, Philadelphia, and Laodicea - see Apoc. i.11. "...Write in a book, and send to the seven churches which are in Asia...." His intent was not to write a tome used to discern the doctrines of Christianity, but to pass along the Revelation given to him by God to the bishops of the early Catholic Church. Do you find similar commands from God to the other writers of the New Testament? Or does your argument rest on this one example, which originally served as correspondence to the churches established in Asia whose existance you would like to deny?
The Scriptures and inherently authoritative.
So are the Koran and the Four Vedas by your rationale. But are they inspired? No, because a Divine Authority has not declared them as such.
The Church, subject to the scriptures, acknowledged what had become universally accepted by the Christian world as the work of the Holy Spirit in writing of certain books.
So the Church was immediately subject to the New Testament Scriptures after Christ's Ascension even as they didn't exist? Or was the Church vested with authority to teach and later compiled the writings of the Apostles to serve as a witness to her Divine Institution?
In the same way the early fathers recognized the powerful and life-giving work of the Holy Spirit in certain writings.
At least now we arrive at convergent opinions. The Church held the Council of Carthage in 397 A.D. to settle the Canon, or unchanging collection, of New Testament Scriptures, which was confirmed by the Roman Pontiff. Up until this time, there had been no authoritative list of which works were genuine and which were spurious. Christian writings were classified prior to the Council in one of three categories: 1) "acknowledged" as canonical; 2) books "disputed" or "controverted"; and 3) books declared "spurious" or false. Much to your surprise, I'm sure, the second category included such writings as the Epistle of St. James, the Epistle of St. Jude, the Epistle to the Hebrews, and St. John's Apocalypse. These books, which you now take for granted as the Inspired Word of God, were disputed amongst Christians and in some place rejected on account of suspect authenticity. Also in the second category were writings such as the Shepherd of Hermas, the Gospel according to the Hebrews, St. Paul's Epistle to the Laodiceans, the Epistle of St. Clement, and others which in some places were put on equal footing with the four Gospels presently found in the Bible. The third category included something like 50 Gospels and 22 Acts which were eventually rejected by the Church as "apocrypha." Without the Church, the Christian world would not have known which writings to accept as "inspired" and which to reject. Thus, Rome spoke, and the Council of Carthage confirmed the unchageable Canon of Scriptures, forever dividing books into the two categories of inspired and not inspired. Without the Church, you would not have the Bible.