I was wondering, can people from the Uk understand Americans?

Hello, I am an American from Detroit mi and I hear a lot of people always saying they can't watch British movies because they don't understand their accents. I never understood that because I love movies and tv shows from the UK (anything with ricky gervais, James Mcavoy, Colin Firth)and I never have a problem with their accents. This started when I was watching green street hooligans with friends. (love that movie) I was wondering, do people from the UK understand Americans? I think I speak with a regular American accent.