I have followed with interest the discussion about 'Unam Sanctam.' I also have read the Catholic Encyclopedia article about it, and have cited to that article in another post. Here is what it says:
""In the registers, on the margin of the text of the record, the last sentence is noted as its real definition: "Declaratio quod subesse Romano Pontifici est omni humanae creaturae de necessitate salutis" (It is here stated that for salvation it is necessary that every human creature be subject to the authority of the Roman pontiff). This definition, the meaning and importance of which are clearly evident from the connection with the first part on the necessity of the one Church for salvation, and on the pope as the one supreme head of the Church, expresses the necessity for everyone who wishes to attain salvation of belonging to the Church, and therefore of being subject to the authority of the pope in all religious matters. This has been the constant teaching of the Church, and it was declared in the same sense by the Fifth Ecumenical Council of the Lateran, in 1516: "De necessitate esse salutis omnes Christi fideles Romano Pontifici subesse" (That it is of the necessity of salvation for all Christ's faithful to be subject to the Roman pontiff)."
Apparently, this has been the 'constant teaching of the Church.' Note the reference to the Fifth Ecumenical Council of the Lateran. As well, the text of the Bull is rich with citations to other Church authorities, including Bernard of Clairvaux. The author was not presenting anything new! Fast forward: I also recall statements in recent years by both John Paul II and Cardinal Ratzinger. The official position of the RCC STILL is that non-Catholics, Protestants like me, are heretics and that in order to have salvation, we must convert to Catholicism and 'accept the supremacy of the Roman pontiff.' That is one of the reasons for the huge concern. Now, if the RCC were to formally recant that teaching, to clearly state that practitioners in other faiths who accept Jesus as Savior may have salvation--which most of the rest of the churches acknowledge, by the way; then perhaps there would be a huge sigh of relief.
Dave