Christianity is not avodah zarah.
Otherwise, we wouldn’t allow doing business with them three days before their holidays.
And, I outlined many poskim who affirm that Christianity is not idolatrous.
The Bnei Noach movement is a fallacy; Bnei Noach is a halakhic categorization for gentiles who believe in G-d and fall under the Meiri’s category of umot that are dictated by the ways of religion. It is NOT a pseudo-Judaism for gentiles, as Habad and other groups have turned it into.