Thanks to satellite and bilingual TVs, as well as DVDs, It's now really easy in Japan to watch program in English.
But don't start off by saying “right, I'm only going to watch TV in English from now on”.
Just like swimming, you don't start by jumping in the deep end of the pool. Start off in the shallow water, just watch one program a week in English, then gradually move on, and eventually you'll be swimming on your own, and be able to watch anything in the original English.
Don't worry if you don't understand it all, I only understand 80% of some American TV shows.
With practice, just a little every week, you soon figure out what the new words mean, and eventually you'll be able to watch any program or movie you like in English, with no problems.