What should I wear to a Catholic church in the U.S.?

Jean & blouses are OK for church, as long as you're not see-through, or showing too low a cut.

You can also wear skirts, dresses, skinny jeans (in my church many of those are allowed), but I dress like I'm going to a dinner, only because that's my style. I like to always look NICE.

Just try to cover up your shoulders

Jeans and a T shirt will do. Jesus never owned a suit

It's pretty much OK to wear whatever (as long as it's not super tight/see-through/showing too much...), although personally I think it's better to dress up a little, you're going to see God, so why not look nice? But honestly, if you wear what you described, nobody'll give you a second glance. Good luck!

A skirt, so the priest will rape you.

Yes. Although some churches are a lot more formal than others, what you describe will work fine for a visitor just about anywhere in the states