I know, I'm just not sure what "American culture is much greater than other culture in popular media" means. Greater how? Says who?

Outsized influence relative to population. Popular media has had a greater influence in spreading American culture than other cultures.

Says me.

Thought it was obvious and conventional wisdom. Feel free to argue the contrary, though.

Other cultures tend to be "americanized" more than the other way around.

Just do a Google search for `americanized india` or `americanized china`.