Moving from Slovenia to SFBA in my mid 20's (~2015) was ... super fun like that. Sooo many people here are that most brilliant super talented engineer/founder/whatever from their home locale. But here we are just the norm.
Then you move or have some experience that opens your eyes and you see that there are so many people out there that you're not actually as special / smart / talented / athletic etc as you thought.
I've had the experience a few times myself, and it's always a bit of an existential wakeup call.
Related - About 10 seconds into my first job I decided that staying quiet for a bit and listening to people around me would be a very good strategy throughout life.
Very similar story here! Grew up in the Netherlands, joined an SV company in my late twenties. Huge mix of imposter syndrome and sadness that I hadn't been able to experience such brilliant people earlier.
Very much regret not choosing different educational paths that could've let me surrounded by them a decade earlier. I would've enjoyed life much more. On the other hand, I don't think either of us could've realized it before experiencing it first-hand, so no reason to beat oneself up over it.