Low tooth visibility when smiling/talking after braces - how can I increase tooth show? (Photos)

Hey everyone. I previously had an underbite and went through braces to correct my bite and straighten my teeth. My main concern now is not that my lower teeth are somewhat slanted. What bothers me most is that my teeth, especially my upper teeth, are barely visible when I smile or talk. When I speak normally, very little of my teeth show, and I feel like this makes my smile and facial expressions look unusual. I would like to increase the amount of visible tooth display if possible. I am really insecure about my smile. What could be causing this lack of tooth visibility? Are there non-surgical treatments that could improve it? I would prefer to avoid jaw or other major surgery if possible.