In his encyclical Testem benevolentiae, Pope Leo XIII warned against those in America who would minimize or change Catholic doctrine in order to be accepted:
- “For they contend that it is opportune, in order to work in a more attractive way upon the wills of those who are not in accord with us, to pass over certain heads of doctrines, as if of lesser moment, or to so soften them that they may not have the same meaning which the Church has invariably held. It does not need many words, beloved son, to prove the falsity of these ideas if the nature and origin of the doctrine which the Church proposes are recalled to mind. The Vatican Council says concerning this point: "For the doctrine of faith which God has revealed has not been proposed, like a philosophical invention to be perfected by human ingenuity, but has been delivered as a divine deposit to the Spouse of Christ to be faithfully kept and infallibly declared. Hence that meaning of the sacred dogmas is perpetually to be retained which our Holy Mother, the Church, has once declared, nor is that meaning ever to be departed from under the pretense or pretext of a deeper comprehension of them." -Constitutio de Fide Catholica, Chapter iv… Let it be far from anyone's mind to suppress for any reason any doctrine that has been handed down. Such a policy would tend rather to separate Catholics from the Church than to bring in those who differ. There is nothing closer to our heart than to have those who are separated from the fold of Christ return to it, but in no other way than the way pointed out by Christ.”
Pope Leo XIII distinguished between two forms of Americanism. Americanism was approved if it “designated the characteristic qualities which reflect honour on the people of America, just as other nations have what is special to them; or, if it implies the condition of your commonwealths, and to the laws and customs prevailing in them, there is no reason why we should deem that they ought to be discarded. But if it is to be used not only to signify, but even to commend the above doctrines, there can be no doubt that our venerable brethren, the bishops of America, would be the first to repudiate and condemn it, as being especially unjust to them and to the entire nation as well.”
 Leo XIII, Encyclical Testem Benevolentiae (1899).