There is nothing wrong with using RCC, except that it may infer she is a real church, which Rome rejects most Prots as being, and i am sure those in the SBS do not mind that use either.
The Church holds that there is one church and all who are baptized in the name of the Father, the Son and the Holy Spirit belong to it.
Protestant/non Catholic Christians are our brothers and sisters in Christ.
It is not that the Church rejects Protestants, it is that she rejects the notion that there is more than one church.