I'm not sure you'd find a disagreement from me in regards to a preference for Judeo-Christian American culture versus other (Saudi, etc). But if the true end goal of our actions is to maintain the Judeo-Christian majority culture, then we as a nation should be honest about that.
We also must recognize our actions in this regard. You mentioned the Dalai Llama being chased from his homeland. The Chinese will mention chasing an entire native population group out of their homeland - America fulfilling its manifest destiny. Our essential American nature is an incredible thing (and often very generous), and also powerfully destructive.
But let's not explain away the actions we take (and the intention to keep our culture in its current iteration) under the guise of safety/security or otherwise - especially when its highly questionable to actually have a net effect of increase in safety at all. Just call it what it is.