Can't stir up nationalism against people who have been brutalized and dominated by US for centuries. They are utterly subservient.
China can only stir up nationalism when it has strong enough military presence to back up these countries against US aggression. Otherwise, these countries will likely remain subservient.
Social Media and Media entities themselves would be controlled directly or indirectly by the US. So shovelling money into an influence campaign is akin to shoveling it into a furnace.