Since American independence, the "Catholic" hierarchy in the United States always possessed a liberal tendency. The first bishop of the United States, John Carroll, was committed to Thomas Jefferson’s principle of separation of church and state.  Since Carroll, American "Catholics" have been generally liberal regarding Church-state relations. 
Broadly speaking, a liberal may be defined as one who, consciously or not, accepts the ideals of the French revolution. Embracing its motto of “Liberty, Equality, and Fraternity,” liberals also embrace the principles flowing from it, including the separation of Church and state and the equal treatment of all religions under the law.
Liberalism has been repeatedly condemned by the Church. When the French Revolution broke out, its leaders laid down the principles of liberalism in the famous Declaration of the Rights of Man. This document was formally condemned by Pope Pius VI (1775-1799).  Pope Gregory XVI (1831-1846) explicitly condemned Liberalism in his Encyclical Mirari Vos.  Blessed Pope Pius IX (1846-1878) further condemned liberalism in his allocutions, briefs, encyclicals and in his Syllabus of Errors.  Pope Leo XIII (1878-1903) stated that “many there are who follow in the footsteps of Lucifer, and adopt as their own his rebellious cry ‘I will not serve,’and consequently substitute for true liberty what is sheer and most foolish license. Such, for instance, are the men belonging to that widely spread and powerful organization, who, usurping the name of liberty, style themselves liberals." 
The first “Catholic” President of the United States, John F. Kennedy, stated that he believed in a “separation of church and state” that is “absolute” where “no Catholic prelate would tell the president (should he be Catholic) how to act…”.  Kennedy’s example has since been followed by many other so-called Catholic politicians since then who have supported abortion, contraception, divorce, embryonic stem cell research, euthanasia, and homosexual unions masquerading as marriage, etc. etc. ad nauseum. Like Kennedy, these politicians have chosen to ignore the Church’s teachings. And like Kennedy, they’ve been rewarded for it.
Even though the Church has a vast tradition opposed to the liberal error of religious freedom, the American bishops do not seem to care. Just this past year the United States Conference of Catholic Bishops (USCCB) once again openly supported the modern idea of religious freedom.  This was part of a long series of compromises that American “Catholics” made with liberalism before this election.
“Catholic” support for Barack Obama is but the latest in this series of compromises with liberalism. But will it be the fatal compromise? As Scripture says, “For what things a man shall sow, those also shall he reap. For he that soweth in his flesh, of the flesh also shall reap corruption.” 
 T. Bokenkotter. A Concise History of the Catholic Church 368 (2005).
 F. Sarda Y Salvany. Liberalism is a Sin 52-63 (1886).
 Leo XIII, Encyclical Immortale Dei (1885) 14.
 See www.americanrhetoric.com/speeches/jfkhoustonministries.com.html
 See: http://usccb.org/issues-and-action/religious-liberty/our-first-most-cherished-liberty.cfm
 Galations 6:8.