"Does he say that when the American Catholic Chuch went, it didn't go alone??"

Answer: Nope! Better still. Here's what United Methodist Church minister Dean M. Kelley tells us himself in his book Why Conservative Churches Are Growing, A Study in Sociology of Religion. New York: Harper & Row, 1972.

Page 90:

"Another reason for the rather precipitate decline of the mainline Protestant churches in the United States at this particular time may be the triggering effect of the sudden discrediting of the formerly unshakeable Roman Catholic Church.

"At least one great church was deemed to know its business, even if others didn't; now it too was seen to falter, waver, and stumble.

"With it fell many lesser churches."

Humm ... sounds like the man is indeed telling us something !!