The reason its considered acceptable to protest and make fun of Christianity in America is because theyre the only organized religion with any appreciable power. Jews and Muslims have no real power here and arent trying to force their archaic beliefs on the rest of us through legislation.
In addition, Jews and Muslims often face real, tangible persecution here. You know, the kind that Christians like to pretend they deal with. Thats another obvious reason that shitting on them even more is frowned upon.
Being the majority religion in this country does not come with "appreciable power". This country is a democratic-republic with freedom of worship and a separation of church and state that I think works very well. The government is not persecuting any religion; what however is happening is the fashionable social-griefing of Christians. What /federal/ legislation are powerful Christians forcing through?
Surely you arent really this clueless. Christians have been pushing for religious freedom acts at both the state and federal levels. Their effect is to allow Christians to freely discriminate against gays and other groups they dislike, all under the guise of religious freedom.