unions

Freedom to turn down a religious meeting is already protected unless you're working for a religious org where religion is a bona fide requirement like a church, or religious non-profit.

Under current US labor law, however, companies can force you to sit through meetings presenting "their side" of why unions are wrong. If you skipped it they would say it's a disciplinary matter and there is no protection. Unions have been pushing, rightly so, for this. As soon as a union campaign or vote is announced, employers spend ungodly amounts of money hiring(money they previously refused to spend on your comp and benefits) anyone they can to assure you why a union is wrong. They can't legally lie, but they sew doubt about what unionizing can bring you(again and again and again) bordering on intimidation which is also legally forbidden, and if you aren't familiar with the process as an employee as most aren't, it's a scary position to be in. It's derailed enough campaigns unions know it need to be stopped and corporations are or course are hoping to take it to ~~their~~ the supreme Court.