One thing I've learned a tutor that teaches American English that it's very common for students wanting to learn how to speak American English... only half of them actually watch American English TV shows or Movies. Some only watch/listen to BBC. If you only watch BBC or maybe watch one American English tv show on a rare occasion.... like in the background when you're doing chores... then that isn't going to improve your American English speaking. Find a show that interests you. Two I suggest is 'Friends' and 'Seinfeld.' You could also try 'The Office.' And watch those on a regular basis. Start with using subtitles if you have to.