Years ago, when I taught a class which involved looking at all the heresies, called the "isms" class by my students, one of the heresies we studied was that of Americanism.
This heresy was defined and condemned by Pope Leo XIII in Testem Benevolentiae Nostrae, which may be found here among other places.
Part of the heresy is accommodation to the world. Another part is that Rome does not understand America. In 2007, as a run up to the elections and the presidential election of 2008, I did a serious study on this heresy. One of the shocking things I discovered was how many bishops were actually involved, and how many dioceses, even those west of the Mississippi, were infected.
Here is a key paragraph from the encyclical.
The underlying principle of these new opinions is that, in order to more easily 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. 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.
Clearly, the spirit of compromise is behind this heresy, which has take over many dioceses in the States. Another point in the heresy is that active participation in the Church is more important than passive. In other words, works over prayer and contemplation.
This pope reminds us in this encyclical that the call to perfection involves recognizing that there is a more perfect way--the life of the contemplative. I have referred in the long perfection series that Garriou-Lagrange and others note that this lifestyle is more perfect. Sadly, this has not been taught consistently in the Catholic Church in America.
There have always been some bishops, some cardinals, some priests and religious, who have wanted the Church in America to be different than the one, holy, Catholic, and apostolic Church.
It is not. The glory of the Church is that it is universal, and not a national church like the Anglican one, for example. The Church of England lacks the universality, the oneness, and of course, the apostolic nature of the Catholic Church.
Americanism seeks to accommodate itself to the Protestant denominations by accepting false premises of ecumenism. How often one hears in America that all Christian churches "are the same" as they believe in Christ as God. But the sameness ends with the Trinitarian baptism.
I shall write more on this later...