How successful has the Secretariat of State been in dealing with the Reformation?

After the Reformation got into swing and Rome started losing significant numbers of followers Rome responded with the Counter-Reformation. The basic plan was unfolded at the Council of Trent . After the Council of Trent the Secretariat of State was heavily developed to create a diplomatic network of Nuncios. How effective is the Secretariat of State? Would the Protestant movement have been more successful without their machinations?