Do Japanese teens know a lot of Western Culture; do they watch our shows, listen to our music etc.?

Question:

LOL bit curious as to how much they know about us. I

Answer:

It's all relative. Maybe to someone they know a lot, maybe to others, they don't.

Not so much teens, but for adults, there are always people who are some sort of otaku (nerd). That includes being an otaku about any aspect of Western culture. Chances are there's someone in Japan who knows more about some particular aspect of Western culture than you do (a particular band, actor, TV show, etc.)

Some popular songs in the West are popular in Japan too. It's interesting because sometimes bands that aren't so popular in the West will sometimes be a bit out of proportionally popular in Japan. Ever heard of Mr. Big? They're a U.S. rock band. I never heard of them until I went to Japan, where they were quite popular.

Most of the big American movies are popular in Japan too. With both music and movies though, most of it is Japanese. I would say that less than half of the popular stuff is from the West.

Some foreign TV shows become popular in Japan, but again, just a fraction of what people watch.

Japanese learn a heck of a lot more about the West than Westerners learn about Japan or Asia in general. You'd be surprised how ignorant Westerners are about Asia in general until they actually spend some time there. A lot of people have some pretty backward ideas.