I had a tonsillectomy when I was younger, and have always been curious how it changed my voice. In the short term it makes you sound squeeky, but what are the long term changes?

I've tried looking this up on search engines without much success. I thought this might be a good place to ask. :D

Without listening to your voice and performing a stroboscopy, hard to say, but here are a few possibilities:

1) If they were large, removal would definitely change the resonance of your speech (voice would be the same as that's produced by the larynx).
2) Muscle tension dysphonia
3) Vocal cord damage from intubation injury
4) Red herring...not actually because of tonsillectomy but something totally unattributed to the surgery; Vocal cord paralysis & bowing usually forces someone to talk in a higher pitch as the body attempts to stretch and tighten the cords to close them completely...however there are other characteristics including breathy quality before compensation, etc.

Recommend you see a laryngologist.