-—Communism derives its support from Catholics——
Are you talking about Catholic people, or the Church?
I assume you mean the former. Yes, many people in South America who identify themselves as Catholic, are communists. This shouldn’t be surprising, since 80-90% of South Americans are Catholic.
But communism is essentially atheistic, so a true Catholic can’t be a communist. Just ask the Catholics of China or Eastern Europe.
This is not a very important factor. If someone can be a Christian by following 99% of the tenets, the same can be said of Communism. Communism is mainly an economic system with atheism thrown in.
Your point on China is invalid. In general, most Asians do not care for Communism and it has been foisted on them. In case of Europe and Latin America, the people have a natural attraction for Communism.
Catholic church is very much socialist in character and Communism is very close to socialism. So it is both the church and the people. The only reason America is not like Europe is that the American Constitutional Republic was set up by Protestants. If Catholics had dominated the adoption of the Constitution, they would have made it a socialist system.