The following is anything but easy, but my son wrote a college paper (in a state college and his prof was a Baptist minister on the side) about the following and got an A+ on it.
His thesis was that, while protestant groups are not conscious of it, a large portion of what they believe is not really part of the doctrine of their own church, but is a part of a sort of "cultural overlay" resulting from the Catholic roots of western civilization...sort of like the whisper of the big bang which, astrophysicists tell us, is coming at us from all directions.
I can't exactly recall how he did it, but he took some of the faith statements of various churches, then pointed out some of the things they commonly believe that aren't in those faith statements, then pointed out how they are actually part of the teachings of the Catholic Church and have been for centuries, using Catholic references for them.
He included some statements about the Church that were said by non-Catholics including, I believe, Edward Koch, who said something to the effect that the Church is a constant that one can always refer to.
He had a concluding line that went something to the effect that to the West, the Church and its doctrinal heritage are like the Pole Star at sea. Mariners aren't all necessarily heading north toward it, but they do use it to guide their way.
His prof spoke to him after he read it and told my son it really made him think.
It really is true, by the way. I have at times handed a copy of the Catechism of the Catholic Church to a protestant and asked him/her how much of it he/she disagreed with. Other than some specific things about Church structure and the Eucharist, they are hard put to disagree with very much of its immense content, even though not a tiny fraction of it is in the faith statements of their own churches.
But as I recall, it really was a tough topic to work up, or so he said. And too, my son is a pugnacious sort of fellow and was really taking a risk handing that to a Baptist minister professor in a state college.