Real catholic liturgy is quite interesting too.

http://www.youtube.com/watch?v=dApWNfJgGC4

It's a result of http://en.wikipedia.org/wiki/Second_Vatican_Council

Traditionalist catholics are disagree with decisions of Vatican II council. See Society of St. Pius X for more details.

To be more precisely, I have to add two details:

Single-party system is not a prerequisite. RSFSR, for example, used a dual-party system until the mid-1920s, Left SR party and Communist party were in so-called "loyal opposition". Similar system still exists in Nepal, this country ruled by coalition of Unified Communist Party of Nepal (Maoist) and Communist Party of Nepal (Unified Marxist−Leninist);

Single-party doesn't mean that all power institutions are controlled by the party. In USSR, for example, ~50% of deputies weren't members of the party. It was named as "bloc of Communists and non-Party"/"Блoк кoммyниcтoв и бecпapтийныx".

For the Orthodox Church and Buddhism it wasn't so clear. Ideology wasn't the only reason, there were somewhat more pragmatic reasons for such type of activity. Weakening of the morale of opponents through eliminating entity what unites them was one of major reasons. But that's pretty correct for the Roman Catholic Church. "Papism" was seen as unreliable and unsafe element, which brings political instability into the society. That's why russian branch of RCC was destroyed completely by Stalinism followers.

PRC is a socialist republic (based on the principles of democratic centralism), which uses state capitalist economy.

North Korea it's a special case. It's a republic de-jure, but monarchy de-facto. They have own ideology, Juche, which is proposed as "Korean-style socialism".

There are some working orthodox churches and buddhist temples in North Korea. But ~2/3 part of people are atheists here.