Music: UK/US
Movies: US due to the broad scale of it. South Korea, France, and Germany are also strong contenders
Games: The US and Japan have both been able to create some of the most revered and critically adored games of all time. I lean towards Japan since they basically invented the video game industry as we know it today.
Animation: Japan. Anime is such a large portion of the Japanese culture that it manages to escape the stigma that animation is meant solely for children. Despite Japan being better, the US has been able to make many good pieces of animated media: (Archer, Rick and Morty, etc.)
TV Shows: UK/US
Comics: US. Marvel, DC, Archie, Dark Horse, Image Comics and IDW Publishing are huge juggernauts in the comic book business. Belgium, Germany, and Japan have created some great comics, but they have not had anywhere near the same success as American ones have had.
A lot of the US's success comes down to it's gigantic population, but other countries have the same amount of potential to make a product that resonates on a worldwide level.
