I see Vatican II as a culmination of Americanism. Vatican II is sort of like God saying "This is the kind of priest you want, one who won't cause you any fuss or make you feel bad or tell you the truth? Here, have it your way." He didn't impose it on us, we brought it on ourselves. It is the classic example of heaping teachers with itching ears.
But there is just no way it happened overnight like people thought. These guys didn't just come out of nowhere. This is the culmination of a long process. When you read some of the things Cardinal Gibbons said and realize that he spoke for the majority of American Catholics, it is shocking. He would say openly that Catholics do not want any other form of Constitution, that we think this one is ideal -- and people really did agree. Many of them today agree. He also said that Catholics should be allowed to run for politics, despite fears that we would try to turn the U.S. into a Catholic state, because a true patriotic Catholic would never bring his religion to public light that way. He's literally boasting about how good American Catholics hide their religion, and are Americans first, Catholics second.
With this kind of attitude becoming prevalent -- an attitude that is far worse than just being lukewarm, but is a form of denial -- with liberal, Americanized Catholics taking over the globe who were not confessing Christ in their deeds and words, it was only a matter of time before God lowered the boom.
The rot goes VERY far back. And don't get me started on EENS or Jesuits.