Anything by Micheal Jackson goes over pretty well. Even if the song is too long and complicated you can just focus on doing the chorus together
Heal the world We are the world Black or white
These songs are all on youtube can be listened to with or without subtitles.
You can also use I have a dream by Westlife or Abba. I play the Martin Luther King Speech to introduce this one.
Michael Jackson has also performed in Korea. I abandoned the obviously prosocial lyrics idea, that became the theme I ultimately intended. Learn the lyrics to an English language song, then watch a video of it performed in Korea. Thanks for the other ideas, too.
For my grade 1 classes, however, we used 'We're going to be friends' by the White Stripes. The students dug it, and the lyrics generally weren't too difficult. The classes were mixed level, and often, students of different levels paired together to complete the gap fill exercise. If you search in youtube, there's a video for the song with cute illustrations based on the lyrics. So, first we simply watched and listened to this, as a primer exercise. Then we listened twice more (once with a different, single image video and then again with the cute drawings). To the pair or group with the most (or close to it) correct answers I gave Oreos. 2-cookie packages for w300. Not too expensive, and each student pair shared a package. It was also a strong motivator, and many students who were ordinarily quiet or misbehaved gave a good effort.
I ended the class with tongue twisters, some of which I wrote myself and some from a video in which a young Korean guy attempts them. The classes went well.