Just to repeat: my list of links was from a random search of 9 schools and since all 9 have organ, I assume many do. I could keep going but I will leave it to you to look a schools you are interested in, then check for organ.
Sometimes organ is not listed (nor are other instruments, at times) so you can also look for faculty for organ or even student recitals.
The info is listed explicitly as a major in some schools which makes it easy but don’t give up on a school without deeper research.
An “organ department” certainly sounds like it would meet your needs 