JD, Actually, the acepteance of the Trinity is NOT a basis for slavation in the RCC , well at least not according to RCC, it is crucial, in their view, to understanding the relationship between God, Jesus but it is not needed for ones "salvation".
I have to disagree with you on this and I'll explain why. In short, according to the Cathechism of the Roman Catholic Church (RCC) belief in the Trinity doctrine is not only professed but is mandatory. Technically, one cannot be Catholic and not believe in the Trinity. It is inseparable from the unity of the church. In fact, it is so much a part of the faith that to deny it is to deny being a Catholic, and catholicism is their means to salvation. I don't think most people understand how central this doctrine is to Christianity. But this does not mean that "understanding" the Trinity in all of its intricate detail is necessary. If that were the case few would gain salvation.
'The Second Vatican Council's Decree on Ecumenism explains; "For it is through Christ's Catholic Church alone, which is the universal help toward salvation, that the fullness of the means of salvation can be obtained," (Catechism, 234). "The mystery of the Most Holy Trinity is the central mystery of Christian faith and life. It is the mystery of God in himself. It is therefore the source of all the other mysteries of faith, the light that enlightens them. It is the most fundamental and essential teaching in the "hierarchy of the truths of faith." The whole history of salvation is identical with the history of the way and the means by which the one true God, Father, Son and Holy Spirit, reveals himself to men "and reconciles and unites with himself those who turn away from sin"' (ibid., 69, 70).
Economic Trinity is inseparable from salvation. “Economic” refers to “divine management of earthly affairs” (The Encyclopedia of Religion [New York, Macmillan Publishing Company, 1987], 54) (Encyclopedia of Religion). “It is oriented to the concrete history of creation and redemption: God initiates a covenant with Israel, God speaks through the prophets, God takes on flesh in Christ, God dwells within as Spirit” (ibid., 54). It is also called revelatory Trinity because the triune God reveals himself through his dispensation of salvation (Trinity and the Kingdom, 151).
"Before receiving the [baptismal] sacrament, [Christians] respond to a three-part question when asked to confess the Father, the Son and the Spirit: "I do." "The faith of all Christians rests on the Trinity."(Catechism, 69). The Trinity is at the very root of the Church's living faith..." (Ibid, 74).
"The ultimate end of the whole divine economy is the entry of God's creatures in to the perfect unity of the Blessed Trinity." But even now we are called to be a dwelling for the most Holy Trinity," (Ibid., 77, 78). "By the grace of Baptism "in the name of the Father and of the Son and of the Holy Spirit," we are called to share in the life of the Blessed Trinity..." (Ibid., 79). "Now this is the Catholic faith: We worship one God in the Trinity and the Trinity in unity," (Ibid.).
So as you can see, the Catholic church's belief in the Trinity is fundamental and essential to salvation. It defines God's work of salvation, His economic mission with respect to redemption.
"The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church and claims over a billion members, representing approximately half of all Christians ..." (Wikipedia). Among Protestants (defined loosely) "There are "over 33,000 denominations in 238 countries" and every year there is a net increase of around 270 to 300 denominations. According to David Barrett's study (1970), there are 8,196 denominations within Protestantism.There are about 800 million Protestants worldwide, among approximately 2.2 billion Christians." (Wikipedia).
Based on these figures, then, Catholics represent a majority of Christians, or close to it, and therefore belief in the Trinity (not complete understanding) is a prerequiste to salvation for most Christians. How many Protestant denominations feel the same way? Hard to say, but if anyone has those figures I would like to see them. I would suspect it is substantial given the fact that “Although a few distinct doctrinal changes were eventually made, the Trinitarian concept emerged relatively unchanged. “The Reformers,” states the New Schaff-Herzog Encyclopedia of Religious Knowledge, “stood upon the ground of the Church catholic” in this matter. This meant, for many of the new-born Protestant groups, not only continued adherence to (and propagation of) the form of Trinitarianism advanced by the Athanasian Creed, but also - in many cases - actual approval and acceptance of the Catholic-spawned Creed itself” (Concepts, 14; in accord see the New Bible Dictionary, 1299-1300).
I hope this helps.