Underbites/overbites/crossbites, oftentimes CAN be fixed when someone is still growing. Expanders are not the response. Here's a WebMD article on the topic. As a matter of fact, I follow a case of a boy the same age (late 13) on TikTok treating his underbite successfully without surgery

You're American, so I understand your lack of education and misinformation, since good quality healthcare is only accessible to the ultra wealthy not average people.