If so, why do they insist in making a distinction between "Christians" and "Catholics" instead referring to all Christian denominations as Christian?
Most of them that I know speak of believers and unbelievers in all churches.
Christians and non-Christians, if you will.
Jesus himself revealed via parable that there would be both wheat and tares.
The protestant reformation, though, is a specific historic event and many of today's denominations had nothing to do with it. They had no dog in that fight.
It is inappropriate to call them protestants. They aren't protesting, nor have they ever protested, the Catholic/Protestant issues of the reformation.
They just aren't organized that way, nor do they think in those terms.
Because in some places -- the Los Angeles area, in particular, where there are an estimated one million evangelicals -- many of these people were nominally Catholic BEFORE their Christian conversion experience. They became Christians in an Evangelical context ("Protestant", if you insist), and their memory of their Catholic past is simply one of spiritual deadness -- "How come they never taught me any of this in the Catholic church?? It never made any sense to me, til my neighbor invited me to Bible study, and then... !!! "
They don't identify by denominations, because they soon meet others who have had similar conversion experiences, in the ranks of the Baptist, Assembly of God & other Pentecostals, Calvary Chapel, Vineyard, etc, etc. They immediately sense a spiritual kinship with others despite the differences of church names (and minor issues, such as tongues, the rapture date, etc). As a result of their easily recognized commonality of spirit, they are loathe to distinguish themselves from one another based on denominationalism, which is increasingly regarded as sinful. So they simply say, "Christians", as a catch-all name for the whole group. And they all listen to the same radio stations and go to the same Christian bookstores and concerts and dating websites.
Some Catholics will go into a rage at this supposed Protestant "sheep stealing", but, the cold hard fact is that the Catholic church, in many places (especially here in Mahoney land) is not doing the job -- they're not evangelizing nonbelievers and they're not even making believers of people BORN into their church! Instead, they sit back and let people blunder along the hellward road until a "Protestant" preacher or neighor or friend takes the time to present the personal call to repent and be saved. Not all of then join Protestant churches, either -- I know a guy who is drawn to the Evangelicals but feels compelled to stay within the Catholic church for family reasons, and I'm sure there are many others like him who stay Catholic but secretly owe their faith to the "Protestants".
I guess you might say, we are PROTESTING against the fact that the Catholic church didn't bother to teach us how to live Christian lives. Fortunately this may all change soon. B16 proclaimed a while back that "lack of Biblical spirituality is the root of Catholic problems", or something to that effect. If he follows through on that idea, millions of Evangelicals may return.
My wife grew up in a "good Catholic" home, and now looks on the Catholic Church as containing the truth but making finding it like finding the proverbial needle in a haystack with all the extraneous additions that obscure it.
We attend a Bible church, as we want to cut to the chase and don't need the fancy liturgy and layers of authority, and frankly find the notion of a man being infallible silly.
I have no doubt there are Catholic Christians (using the term as in the Bible to mean those who have accepted Christ as Savior and are born again), but from my considerable experience with Catholics I've found most to be more concerned with going through the motions of worship and culture and ignorant of and/or unconcerned about a personal relationship with Christ.