Rethinking who we're Protesting

Several months ago a Catholic friend of mine, who considers himself to be a Catholic evangelical, challenged me to find out where the Catholic Church teaches something contradictory to the Bible. As I've been discussing my investigation with several friends, most of whom are in the PCA, I realized that anti-Catholic sentiment runs very high in PCA circles. This makes sense because the Catholic Church teaches that God's grace is infused and transformative whereas Reformation theology rightly understands that His grace is imputed and declarativive (and also infused). This is no small difference, but it is the most substantial disagrement between the PCA and the Roman Catholic Church.

What's interesting is that the PCUSA (the largest Presbyterian body in America) has denied the inerrancy of Scripture, has ordained women to every office, has denied salvation by Christ alone, has ordained non-celibate gay pastors, and now permits babies to be baptized in the name of the "Mother, Womb, and Baby." The Roman Catholic Church, however, upholds the inerancy of Scripture, salvation by grace alone through Christ alone, does not ordain women to Church offices, and publically teaches homosexuality to be a sin. My question is simply this; who do we have more in common with? The PCUSA or the Catholic Church? If we have more in common with the Catholic Church, then why don't we refocus our Protestation on the PCUSA instead of Rome?