If you ask your average Evangelical Christian, including most Baptists, Pentecostals, Reformed folk, etc. they would almost universally say that this distinction… Catholic vs Christian is not only real, it is essential!
This is also holds true for nearly every ex-Catholic, turned Protestant i have ever met. If you sit in on any given evangelical Bible study you are bound to hear the words from ex-Catholic… "I used to be Catholic but then I became a Christian."
If on the other hand you ask a Catholic, is a Protestant a Christian? They will probably answer, "yes," with some reservations. You may hear them say things like, "they are Christians but they need to come home to the church." Most Catholics however would categorically oppose the question raised in this post… Catholic vs Christian. They would be offended by the question because they absolutely consider themselves to be Christians.
So why do evangelicals generally make this distinction?
Although this answer is somewhat simplistic, the rift is rooted in the different ways Evangelicals and Roman Catholics view the doctrine of the New Birth, or Regeneration.
White conversing with Nicodemus in John 3, Jesus announced to the Pharisee that "he must be born again." Here is the full text…
5 Jesus answered, “Most assuredly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. 6 That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. 7 Do not marvel that I said to you, ‘You must be born again.’ 8 The wind blows where it wishes, and you hear the sound of it, but cannot tell where it comes from and where it goes. So is everyone who is born of the Spirit.” (NKJV).
In the same passage, Jesus goes on to talk about the necessity of belief.
16 For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life (emphasis mine).
18 “He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God. (John 3:16, 18, NKJV).
There appears to be two relevant things going on in this passage.
On the one hand, Jesus says that a born-again person needs to be born of the water and the Spirit.
Roman Catholics view regeneration (new birth) as being part and parcel with the Sacraments of Baptism and Confirmation. Belief they would suggest, is a natural part of Confirmation. In other words they would see regeneration more as a process than a single event.
Evangelicals on the other hand focus on belief (and usually only on belief). Furthermore the belief they intend is personal belief and has nothing or little to do with the sacraments of the church.
So what should we make of the original question, Catholic vs Christian: Is it a thing?
What about Catholics... Are the Christian? Of course they are Christian. They aren't Muslim. They aren't Hindu. I never met a Catholic that doesn't confess the Nicene Creed and the Apostle's Creed.
Notice what I didn't ask… Are individual Catholics Christians? I don't know. Neither do you. But the same could be said for any Christian, regardless of the stripe.
Our encouragement for anyone who claims to be a Christian, weather Catholic, Baptist or Methodist should be exactly the same, "Believe on the Lord Jesus Christ and you will be saved."
Perhaps the question then should not be Catholic vs Christian, but rather Catholic vs Protestant.
That would make more sense wouldn't it?