Are cross bite treatments only cosmetic or are there actual medical impacts?

Yes, dental impacts: Of course, it depends upon the severity and complexity of the individual case, but there can exist periodontal and stress related issues with a cross bite. Is there excessive wear, do all teeth occlude properly...? See a dentist or orthodontist. Always consult with two or more different orthodontic offices before starting any treatment.

Cosmetic & Medical: Teeth are designed to take vertical forces. When teeth are in cross bite, the forces are often diagonal or lateral which can be damaging to the periodontal bone support. Oral hygiene may be much more difficult when teeth are out of alignment, also contributing to dental disease and the systemic medical problems associated with periontal inflammation and infections.

Malrelationship: If you had one leg 3" shorter than the other would you say the problem was cosmetic or functional? Having a narrow upper jaw is proportionally the same problem. Having teeth alone out oaf alignment can cause major damage. When cross bites are corrected, not only do teeth and jaws function better, but they also look better. Please see an orthodontist for an opinion.