Democracy is based on simple freedoms. Freedom of Relogion is one of them. Freedom of religion is also fundamental for the US constitution.(https://www.Law.Cornell.Edu/constitution/first_amendment). What kind of democracy it is when som people can tack away fundamental freedoms from other? Even if they are your parents, onebody can tack freedoms form other.
I started of at Seventh Day Adventist church with my nan but she changed to Anglican after 2 years at SDA. She has forced me to leave with her even though I have told her I don't want to. I have no rights to uphold my own religious beliefs. On top of this I have a girlfriend at the Seventh Day Adventist with mental illness in which I can't be with on the day which makes her the most happiest which instead makes her really upset. I have become seriously depressed as a result of this too and my spiritual journey is dwindling. I'm only 17 but should be allowed to choose my religion.
If you're still living under your parents roof, then it's best to be neutral with no opinion while you secretly disagree with their religious beliefs. A neutral position is a respectful position by default.
Meanwhile, understand that your parents want to raise you with particular qualities. Such qualities would include religious beliefs because those beliefs express and reflect what they believe a moral character should resemble. Rejecting your parents teachings and practices openly is a direct disrespectful insult to your parents, which you want to avoid because you love them.
After you get a job and move out it becomes a different story. You're building your own nest then. They have to respect your beliefs just like you did theirs for 18+ years.