By the way, as long as you pointed out the PCUSA/PCA split, it may interest you that while I attend an English-speaking congregation of the Associate Reformed Presbyterian Church, the rest of my family attends a Korean-speaking congregation of the Presbyterian Church in America whose pastor speaks very little English. We also have a fairly conservative PCUSA in this area whose pastor is an evangelical and I've visited there occasionally, but I would not join it due to the apostasy of the denomination.
Rick Santorum’s speech is **NOT** attacking Protestantism in general, but rather attacking liberal Protestants who have denied the Gospel. If people kept digging into Santorum’s speeches, I would not be at all surprised if he's said some severely critical things about liberal Roman Catholics as well.
As a conservative Catholic, I assume Rick Santorum affirms the decrees of the Council of Trent which severely attack Reformation doctrine. That means Santorum and I have major theological problems with each other. I affirm Heidelberg Catechism Q&A 80 and its statements about the Mass, and while I am less familiar with the details of the Westminster Confession and Catechisms, I certainly have no problem with their pretty strongly anti-Catholic doctrinal affirmations. (Side point: I'm more familiar with the Heidelberg because spent most of my adult life in the Dutch Reformed world, and my local church was once a Dutch Reformed mission church before it left the URC and joined the ARPs. My wife's church was in the early stages of joining the Christian Reformed Church before the women's ordination and homosexuality issues blew up in the CRC, and they decided to join the PCA instead of the CRC.)
But that's not what Santorum was talking about when he was attacking mainline Protestantism.
Conservative Catholics and evangelical Protestants have been working together in the pro-life movement for at least four decades. We've pretty much figured out how to agree to disagree. And we both have very little use for the liberal elements in our churches which seek to pervert the faith.
I happen to agree with you that Rick Santorum was referring to liberal Protestants who have denied the Gospel.
But I'm not sure why you want to get into the doctrinal differrences between his Catholicism vs Protestantism.
Already a huge number of Protestants...Evangelicals....have searched their hearts and with discernment have chosen to support him.