I live in Pennsylvania. Is there a building code that states if you have to
have a window and/or a vent in a full bathroom or a powder room (no
tub/shower)?

If you are CREATING a bathroom then the new bathroom must have
either a window or a mechanical vent. There is a not-so-subtle
difference between that and saying that you must have such
ventilation in all bathrooms.

I can't see why this should be a problem, though. If the
toilet fixture can be vented, so can the room it's in.