Yes, which makes me believe that you are legally protected from being fired for publicly expressing your affiliation with a religious group. However, you are not protected from being fired for expressing political views, regardless of whether they stem from the religion you are affiliated with or some other source.
This is just an armchair lawyer level of reasoning on my end here, I have no idea if this is how it actually legally works, but that sort of makes sense. So if someone with the actual knowledge can chime in, that would be appreciated.
this whole cancel culture I think has taken a turn for the worse in the recent past.
Well yeah, but they can be, and their employer won't get in any legal trouble. Having controversial political statements on your tshirt doesn't mean that you will get fired or that you deserve to be fired, it means that your employer has a right to fire you for it with zero legal repercussions. And if the employer doesn't want to fire you for your political statement, they won't, it's up to them.