Source please?
Since many Protestants are members of the church of Jesus Christ they are therefore Catholic.
Sorry. This dog won't hunt. I've been to Protestant Churches when the Nicene Creed was recited - "... one, holy, catholic, and apostolic church" - wouldn't want to get confused with those "Roman Catholics." I even knew a Presbyterian minister who noted in a sermon that he is catholic - but emphasized the lower-case 'c' part.
Merriam:
Main Entry:
Cath·o·lic
Pronunciation: \ˈkath-lik, ˈka-thə-\
Function: noun
Date: 15th century
1 : a person who belongs to the universal Christian church