Jeremiah 31:30-36
Augustine doesn't represent ALL of the west... and he never did.
"BE it known (and without doubt) unto you, that we all, and every one of us, are obedient and subject to the Church of God, and to the Pope of Rome, and to every godly Christian, to love every one in his degree, in perfect Charity, and to help every one of them, by word and deed to be Children of God: And
other obedience than this I do not know to be due to him whom you name to be Pope; nor by the Father of Fathers to be claimed or demanded. And this obedience we are ready to give and pay to him, and to every Christian continually. Besides, we are under the government of the Bishop of Caerleon upon Uske, who is to oversee under God over us, and cause us to keep the way spiritual.
...
Austin {Augustine} having met with this affront, and perceiving that the Britons were stronger in their Faith than he by his Miracles, cast about to try the Saxons courtesie; that what the Ephod could not, the Sword wrapt up therein should. I say not that he procured, but
he threatned or prophesied the destruction of the Monks of Bangor; and it came to pass, and the accasion by writers loudly suspected."
--Nathaniel Bacon, An historical and political discourse of the laws & government of England
https://quod.lib.umich.edu/e/eebo/A59082.0001.001?rgn=main;view=fulltext
So... Britain may have been the first protestant church... if not for the fact that Augustine {Austin} came after the Gospel was already planted in Britain.
This is why Pelagius the Briton was called a heretic... against the Papacy.
"In these words of Pelagius (ad Demetr. 2 init.) we recognize distinctly his moral temperament. (a)
God has commanded man to do that which is good; he must, therefore, have the ability to do it. That is to say, man is free, i.e., it is possible for him to decide for or against that which is good: “But we say that man is (always) able both to sin and not to sin, so that we confess ourselves to have always a free will" (Pel. in his confession)."
--Seeburg, Text-book of the History of Doctrines
Galileo was also called a heretic...