The Catholic Church has had many groups break away from it over the centuries, besides the protestants. One such group is the Polish National Church which seems to have been started in 1897 as a result of harsh treatment of Polish Catholics in the United States by the Church hierarchy and issues of parish ownership. In 1984 a dialogue was started between the Catholic Church and the Polish National Church and in 2006 a Joint Declaration on Unity was issued. Locally, there is a Polish National Catholic Church on Long Island - St. Francis in East Meadow. This is one of many examples of Christians breaking apart from one another and at the least we should be working to be as united as possible despite differences in practice, theology, ecclesiology, and worship. It also shows that, despite the Church being at a height of cultural influence and internal strength in the decades from the late 1800's right up to the 1960's, there were problems that caused divisions and break away groups. At least since Vatican II, the Church has been attempting to dialogue and unite closer with all groups and there has been some success.
Excerpt from the Joint Declaration:
"In response to an inquiry from the Archbishop of Baltimore, His Excellency William Keeler, then President of the National Conference of Catholic Bishops, His Eminence Edward Cardinal Cassidy, President of the Pontifical Council for Promoting Christian Unity, stated in 1993 that members of the Polish National Catholic Church in the United States and Canada may receive the sacraments of Penance, Holy Communion and Anointing of the Sick from Roman Catholic priests if they ask for them on their own, are properly disposed and not otherwise excluded from the sacraments in line with the provisions of canon 844 �3 of The Code of Canon Law. This was followed in 1996 by a letter by Archbishop Oscar H. Lipscomb, the Chairman of the Bishops' Committee for Ecumenical and Interreligious Affairs, to the bishops of the United States spelling out in more detail the conditions under which Polish National Catholics may receive the aforementioned sacraments in the Roman Catholic Church. In 1998 the Polish National Catholic Church issued Guidelines for the Reception by Polish National Catholics of Sacraments in the Roman Catholic Church. Canon 844 �2 of The Code of Canon Law also specifies conditions under which Roman Catholics may receive the sacraments in the Polish National Catholic Church."