But wouldn't you say that paganism corrupts all religions?
However, I do think the historical connotation was toward the Catholic Church. The Letters to the Churches by John in Revelation are an excellent indication that paganism has been around forever!
(Yes, I know there are examples even before the time when Revelation was written.)
In America, paganism has chipped away at all faiths. Plenty of articles and exxamples to show that, from not holding a worship service on Chirstmas (large Protestant non-denominational church) to weirdo masses in certain dioceses.
I don't know about corrupting it. Although Catholics and many Christians celebrate the birth of Jesus on Dec 25, we're still celebrating the birth of Jesus, not the death of the Snow God or whatever previous festival took place at that time.