The Americans produce more movies so you are used to hearing more American English accents than British English ones.

As it appears to me the American pronunciation, say accent, has emanated from a universal blend of accents. So, native english speakers have contributed to the American Accent; German native speakers have contributed to it as well; likewise, Spanish, Dutch, Portugese, Chinese, Afro-american, Greek and Jewish accents have have contributed to the final blend of the 'American English' accent and context. Therefore, the Latin-Greek vowels which are loud, very distinct and accurately transcribed from text to speech and vice versa have seemingly dominated in the 'American English' accent against the whispering vowels of most native English accents which have developed long before the final establishment of the Late Middle English script. Personally I adore the quietness and discretion of the low loudness of British accents although 'American English' accent is much easier for me to pronounce and understand when communicating with universal English speakers.

It's not. Both are equally difficult.

As a non-native English speaker and a native Korean, for me, British accent is much easier. I think that's depend on your mother tongue that helps you speak a certain accent easily.