I allude to the fact that the Roman Church has ever striven for and possessed temporal power.

The Catholic Answers

Remember that the Church has to exercise the authority of Christ in this world. To do this, she needs to be free to deal with Catholics of every nationality, Riid therefore to bs free from the political interference of any particular nation. Now she can be free either by being independent of all rulers, or by being subject to a king who guarantees absolute liberty of action at least to the Pope. Kings, however, have ever been jealous of their authority, and prone to abuse it. If they grant freedom, they always regard it as being by privilege, and there is ever the danger that, if they happen to be displeased, they would try to interfere in Church administration. Hence God’s Providence arranged that certain early kings legally donated territory to the Church, rendering her independent of earthly authority altogether. After hundreds of years these states were illegally taken from the Church, and she certainly protested.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty