You are saying exactly what OP is saying but just rephrasing it another way.
The more a movement crosses borders, the less likely it is to be based on the needs of any particular country and the more likely it is to be based on the needs of the transnational billionaire class.
Drinking age is not the only example, driving age is another good example and also the old TV rating system. What was considered taboo in America was often at the same time considered to be fine in places like Europe, or vice versa. But we never had a coordinated international push for censorship when it came to TV/movies like we are seeing with social media.
I can remember how much people used to deride mass surveillance and censorship in places like Russia and China and now here we are very quickly catching up to them in every way.