I agree with Sandra gracefull a true American buttercream is made with either all butter or half butter and shortening. I don’t know when ABC was ever designated as strictly all shortening icing. I have a ABC recipe from a 1970’s Wilton cake decorating book, and it calls for all butter. And half & half butter/shortening icing for warm weather.
Creativity is God's gift to us. Using our creativity is our gift back to God. Clarky's Cakes 😎