Edits found to late:
"[B]ut is probably closer" should be "but which is probably closer."
And I'm right, my grammatic is wrong. I'm sure of it. It's "The Assemblies of God is," and not "The Assemblies of God are," since "Assemblies" (a plural) is not the subject; "Assemblies of God" is, and that is a singular noun, the name of a single denomination!
What may be surprisin are some of the other denominations in decline. Southern Baptists (2nd) are down again,
In the South we spell it surpirsin' with an apostrophe.