On January 22, 1899, Pope Leo XIII addressed an encyclical (Testem benevolentiae nostrae) to James Cardinal Gibbons, archbishop of Baltimore, intended “to suppress certain contentions” that had arisen in America “to the detriment of the peace of many souls.” In essence, Leo feared that some American Catholic intellectuals, including a number of bishops, were finding canonical and theological lessons for the Church where they should not be looking for them: in the American cultural and political experience of democracy and individualism.
“The underlying principle of these new opinions,” wrote Leo,
is that, in order to more easily [sic] attract those who differ from her, the Church should shape her teachings more in accord with the spirit of the age and relax some of her ancient severity and make some concessions to new opinions. Many think that these concessions should be made not only in regard to ways of living, but even in regard to doctrines which belong to the deposit of the faith. They contend that it would be opportune, in order to gain those who differ from us, to omit certain points of her teaching which are of lesser importance, and to tone down the meaning which the Church has always attached to them.
Leo named this heresy Americanism, after the country that had spawned it. Debate continues to this...