Evangelicals and C.S. Lewis

This evening on the way to the evening service at church, my friend who's from Northern Ireland asked my opinion of an interesting phenomenon he's noticed. Evangelicals in the U.S., he points out, generally love the writings of C.S. Lewis, and look to him in many respects as something of a spiritual mentor or guide. Lewis, however, was not himself an evangelical, and had some theological views that most evangelicals today would find troubling. In Britain, it seems, most evangelicals are aware of this, and while they might appreciate some of Lewis' works, they wouldn't nearly treat him as much of a patron saint as Americans do. Why, then, is it that your average American evangelical would probably tend to trust Lewis as someone whose writings are generally faithful to Scripture and trustworthy?

I have enjoyed several of Lewis' works myself, and I appreciate the gift of clear, thoughtful, imaginative communication that God clearly bestowed on him, but I'm curious about this. Is it that American Christians are generally fairly theologically ignorant and undiscriminating? Maybe the average member of Wherever Bible Church wouldn't expect to get along with an Episcopalian spiritually, but, not knowing much about Lewis' affiliation, doesn't know or care enough about theology to know problematic material when he or she reads it?

I'm just musing here, and I'm curious to know what others think. Why do you think American evangelicals regard Lewis so highly?