In my view it's the language. English is so common everywhere that young people around the world are pretty good at it (including me), so they get onto the internet from a young age and start consuming English (mostly US) websites, social media, and movies etc, which further strengthens the grip the US has.

Meanwhile, you'd struggle to find an American, or any one from the Anglosphere really (maybe with the exception of Canada) who speaks Greek, French, Arabic, Vietnamese, etc.