There are two Saints Augustine – the bishop of Hippo, and author of the Confessions and numerous other theological masterpieces, and, today’s saint, Augustine first bishop of Canterbury, (+604), often pronounced in England, ‘Austin’. Both were Roman citizens, for there was but one civilization and one ‘world’ in those days, united by the Faith. So too, there was one Church to which they belonged, which was the source of that culture: Hence, Roman and Catholic.
As Hilaire Belloc points out, the notion of ‘nations’ came much later in history. There was the Church, and then there were the pagan, the un-civilized, the barbarians – the yet-to-be-redeemed. We were then a long way yet from Rousseau’s imaginary dreams of noble savages as the ideal of Man.
Also, there were no ‘denominations’ of Christians, and, as Newman discovered in his own historical research, England’s Anglicanism did not come to be until after Henry VIII, its progenitor; as the Oratorian put it, to delve into history is to cease to be a Protestant. England was Catholic, and much of that is owe to Augustine of Canterbury.