In 538 AD, the Catholic Church was the ONLY Christian Church.
There have always been small heretical groups that have grown out of that ONE Church.
From the writings of the EARLY 2nd century – we see that the Church established by Christ and spread by the Apostles was already being called “The Catholic Church” – NOT as a mere description – but as a TITLE.
In an age with NO internet, NO TV, NO Radio and virtually NO Postal Service – it took YEARS to spread the news and YEARS for the name to catch on. St. Ignatius, Bishop of Antioch wrote about “The Catholic Church” at the BEGINNING of the 2nd Century as if his readers knew FULL WELL what he was talking about.
Later, in that same century, we read about “The Catholic Church” – again as a TITLE in the “Martyrdom of Polycarp”, as well as a list of Popes beginning with Peter in Irenaeus’s “Against Heresies”.
By 538 AD, the Catholic Church already had MANY Councils and Synods that had dealt with a great MANY things including the Canon of Scripture, the Hypostatic Union, the Trinity, and heresies like Gnosticism, Arianism, Nestorianism, Montanism, Pelagianism, Manichaeism, etc.
Regardless of what you’ve been spoon-fed at your anti-Catholic meetings - there was only ONE Christian entity in 538 – the Catholic Church.
I suggest you take some time off and do an intensive study of history . . .