l. There never was a united Christendom. True, Roman Catholicism was close to achieving that in western Europe when it had the power to eliminate heretics. But the eastern churches never acknowledged the authority of the Pope in Rome over their dioceses. In the west, Catholicism was able for some centuries to eliminate dissenters through intimidation or by killing them off, as in the case of the Albigenians or via the Inquisition. Just before Luther there were a number of 'heretical' movements, such as the Lollards, the Hussites and the Waldensians. They were oppressed, although the Waldensians managed to survive by fleeing into the hills. A few years ago they united with the Italian Methodists.
2, It's true: liberal Protestant groups have suffered, as more and more US Protestants have either deserted religion or moved to fundamentalist churches. However, a form of liberalism now is very powerful within the Catholic Church USA, almost certainly the majority sentiment among contemporary American Catholics. What also has especially amazed me is the percentage of former Catholics who have left religion entirely, or moved into Protestantism, both liberal and conservative groups. In visiting fundamentalist churches, I have found here in the northeast that the majority of their members would seem to be ex-Catholics. I have tried to figure that out. Any thoughts? In Connecticut, for example, the Catholic percentage of the population, according to a recent study, has dropped from 47% to 38%. How does one explain that?
3. The notion that conservative Protestants are more likely to believe in the Real Presence than liberal Protestants seems to me to be questionable. What may be true is that many conservative Protestants take communion more seriously than many liberal Protestants. This may be especially true among African-American Protestants, a quite high percentage of the Protestant population in the US (probably 20%-25% or even higher). On the other hand, I have found communion much more casual, even fleeting, in many evangelical congregations. So it's a mixed situation, defying generalization until more study is done. Incidentally, the Latino percentage of US Catholics is approaching 40%, though Protestant fundamentalists are busy and quite successful among them.
4. The main obstacle to unity between Catholics and Protestants probably can be summed up as 'freedom'. This freedom has many components. Freedom of belief, without a compulsion to believe this or that doctrine that they may find unbelievable. Freedom to interpret scripture as they feel led. Freedom to debate matters of faith without being told that there is only one true view on the question and any other is heresy. Freedom of the Protestant clergy to marry and have families. Freedom of married couples to plan their families with the use of modern methods of birth control. Freedom from a 100% male hierarchy that governs the church, while Protestants treasure the central role the laity plays in running local churches. Very few Protestants, whatever their label, would give up this freedom.
But, anyway, God bless Catholics, Protestants, Orthodox - and, yes, Jews, Muslims, Buddhists, Hindus and all of our brothers and sisters of every race and creed and nation. The Catholic Church deserves much credit for its health ministry and reacing out to the poor. Thanks God for Mother Theresa and others. Let us work together to heal the wounds of past intolerance and make religion a bridge and not a barrier.