One aspect of the original question that hasn't been touched on yet is the date of easter compared to that of passover. The obvious answer is that Jews keep a lunar liturgical calendar and Christians don't. But it's more subtle than that. In the middle ages the calculation of the date for easter was a divisive issue. The only important Christian group that celebrated easter on the passover date was the Irish church. Since they also rejected the authority of the bishop of Rome (the pope), and for other reasons, their suppression became an important goal. The institutionalized anti-semitism that characterized much of Christian history is probably the main cause of the rest of the differences. It's worth noting that a pope gave the English king dominion over Ireland to 'correct' practices in the Irish church.