Modern Christianity is extremely diluted, yes. To the point where it's indistinguishable from any other ideology that preaches:
a) Altruism. (delusional zealotry, madness, and suicide of reason)
b) The existence of a Supreme Being. (schizophrenia)
Everything else is mere pomp and ritual, play-acting, and gang formation. What a Catholic and a Baptist believe are indistinguishable in all important aspects - yet Baptists and Catholics have been known to fight over those unimportant and pathetic points of contention between the two schisms of their cult. This violence over insignificant scriptural details is why religion is so dangerous. It breeds herd mentality and gang culture.
EDIT: And... this. is. not. a. question. of. personal expression.
The state is secular, therefore it should neither endorse nor dismiss any religion. That is written in your constitution, the thing you Americans seem so enamoured of. Apparently you only call on it when it benefits you to do so. Having any religious icon in a public building would entail endorsing a religion. Is that so hard for you to understand, or do I need to tattoo it on your forehead with a rusty needle?