Hi Pre-optometry student!
I got this one. I attend a catholic university currently for undergrad. Trust me on this one, no worries there. Not everyone there is Catholic. My school has a lot international students of all religions. It's a school like any other school. Plus, I'm pretty sure if they did inflict a religion on you that would break American code. I do know they have an interfaith room, where anyone can go for peace/quiet. Its Catholic in the way that the undergrad school was founded by sisters so faith is important to the mission and what they stand for.