The PCUSA is considered the "mainline" Presbyterians. In fact, most times when the word Presbyterian is used in the press, they are speaking about the PCUSA. And yes, the PCUSA has ‘Gone from’ Christianity.
In fact, in most conservative churches I have been in, the word "mainline" is a synonym to "liberal", and the liberal church has definitely ‘Gone from’ Christianity.
Touché!
Exactly! mainline/mainstream=liberal