I am not Catholic but Protestant yet I heartily approve of those who suffered for the name of Christ.
As C. S. Lewis noted, those closest to the center of each Christian communion, are the ones that seem to agree the most in the main.
There can’t be, in the truest sense, more than one universal church. How it manifests on earth is another story. The Roman and Orthodox split-up on earth came well before Luther arrived on the scene. This handicaps the universal church, but its earthly reuniting will need miracle, just as its original creation did.
Each piece bears some tradition of what it once belonged to. Reformation Protestants are yet “Catholic” Protestants. Orthodox have splinter groups that we hear about less.