I once read a book entitled The Catholic Roots of the Protestant Gospel: Encounter Between the Middle Ages and the Reformation (Studies in the History of Christian Thought) by Stephen Strehle. Unfortunately this title is now out of print (I have access to it still though). And yet even the title itself is provocative a certain reality, even for those who follow the New Paul Perspective[s]. As I recall, Strehle works through some of the magesterial Reformers, like Luther, Calvin, Zwingli, and others; and he highlights how the grammar used by the Reformers was language taken from their Roman Catholic forbears.
The point that I want to highlight though is this: the Protestant movement originally is not what it has become today in Fundamentalist and/or neo-Evangelicalism and the Free church movement. The fissure present between Roman Catholics (Eastern Orthodox) and the Protestants I don’t think has changed much over time (except for the distance between then and now); especially in regard to conceptions regarding ecclesiology, and then subsequent thinking on salvation. Nevertheless, this notwithstanding, there remains continuity between Protestants and Roman Catholics insofar as the Protestant church is intended to be a reforming movement within the Roman Catholic church and not without it. What recognizing this orientation does, is that it grounds the Protestant heritage in the historic and orthodox faith of the church that finds continuity with the so called ecumenical councils of the church; the councils that gave us the relative grammar for the Trinity, the hypostatic union of Jesus Christ (God-man), etc.
From what I have observed, the Free Protestant church has absolutized the fissure between Rome and themselves (doctrinally) in such a way that not only have they apparently disabused themselves of the idea that the catholic faith is no longer binding, but they have, in general, presumed that the Roman Catholic church is really a totally different belief framework, such that Evangelicals can speak of Catholics as if they are not even Christians, while they as the Evangelical are.
Really all I am trying to suggest is that such a Pervasive Interpretive Pluralism has taken hold in the American Evangelical church, that every interpreter does what is right in their own eyes (even if this means to begin to question the moorings of the catholic faith, which is the Trinitarian faith).