Yes, Vatican II is the culprit but not exclusively as people who comment on my blog would write. There are in fact three culprits as highlighted by Dr. Bullivant in The Catholic World Report interview which you can read in full by pressing the title above. Below are some money quotes from that interview.
What I have always emphasized Stephen Bullivant confirms. Catholics prior to Vatican II who had a “ghetto” experience of Catholicism (something positive not negative in terms of Catholic identity supported by the community in which one lives) experienced after Vatican II a fragmentation of that community which brought them to an “ecumenical” world of a variety of people and less of a connection with a Catholic ghetto experience. Vatican II’s implementation exacerbated this fragmentation and disengagement from Catholic identity by mocking all things pre-Vatican II and erasing Catholic cultural experiences such as the Latin Mass, nuns in habits, surety of doctrine, uniformity, devotions as well as fasting and abstinence.
Vatican II also demanded engagement with other Christians, non Christian religions and secularism itself as though these were on an equal footing with Catholicism. This helped to erode the surety of Catholic identity and being a part of the “True Church” in which salvation could be experienced and only experienced in the true Church.
The second generation of Catholics living in a not so homogenous Catholic culture became less attached to things Catholic and a strong Catholic identity. Then their children brought up with even a less connectiveness to the Church could take her or leave her and many leave with no real worry about doing so.
Ultimately, though, liturgical changes and the “customs” and little “t” traditions completely abandoned in the 1960’s, to include habits on nuns and Catholic schools filled with nuns escalated the crisis of Catholics who no longer claim to be Catholic either by joining other Christian groups, non Catholic religions or no religion at all (nones).