I just may be slow, but I came across the term "Christianism" in a recent blog post and it caught my eye. The link is here: CHRISTIANISM REDUX.
The concise definition he gives is: "the fusion of politics and religion for the advancement of political goals." Nifty, eh?
Of course, generally speaking, calling most things an "-ism" is a convenient and quite often pejorative way to overgeneralize and brush off opposing arguments. However, this is a useful term I will start using since it's so dominant in American politics and in my opinion, to be avoided in the Church (una sancta for you "dogmatophiles" out there). In other words, I think it's something most people "get," and therefore can be useful for discussion.
Also, if you're wondering what my view is on this, keep in mind my thoughts from a previous post, Is Jesus' Kingdom Political?