What Does It Mean to be in Communion With the Church?

In their relatively recent statement on the Eucharist, http://www.usccb.org/dpp/Eucharist.pdf, the U.S. Conference of Catholic Bishops maintains that Catholics are required to conform their consciences to the Magisterium and they warn that selective departures from the Magisterium “seriously endangers our communion” with the Church. Nonetheless, this seems to suggest that some departures might be consistent with membership in the Church. They proceed to state that those who “knowingly or obstinately” reject the defined doctrines or definitive moral teachings of the Church should refrain from receiving communion because they have seriously diminished their communion with the Church. This too leaves open the question whether rejection of one teaching is fatal or rejection of more than one teaching is permissible and, if so, which ones. Certainly the spirit of the Bishop’s statement seems to suggest that Catholic are to agree or stay away from the Eucharist.

I do not have access to recent statistics as I write this. But American Catholics disagree with many moral teachings of the Church. Between 1963 and 1974, for example, the majority position of American Catholics shifted away from that of the Vatican on issues such as whether sex before marriage was always wrong (from 74% to 35%), whether divorce after marriage is always wrong (from 52% to 17%), and whether contraception is always wrong (from 56% to 16%). The same can be said of American Catholic priests. The Vatican , for example, maintains that homosexual relations, masturbation, and artificial birth control are always wrong, but only 56% of priests agreed with the  Vatican’s teachings on homosexuality, 28% on masturbation, and 25% on birth control.

What would happen if the Conference made a statement with no wiggle room,  maintaining that if you did not agree with the Vatican on all of the issues above and many others, you should not receive the Eucharist (or say mass if you are a priest)? I am uncertain about what the relevant priests would do. But regarding the lay population I suspect a small percentage would stay in the Church and not partake in the Eucharist. Many would leave the Church. And most would simply ignore the Bishops.

I am curious what people think. Assuming their attempts to change minds about morals are for the most part futile, should the Bishops try for a smaller American church filled with people who agree with what they take to be the truth? Could they achieve a church that was homogeneous in belief even if they tried? Why are they not trying for a smaller church? The Vatican won't let them? They don't want it? Alternatively, is the Holy Spirit using the People of God to tell the Bishops something that they do not yet get? Or have the Bishops struck the exact right note?