Im not english mother tongue and i have a question about accents?

ive been watching some american tv shows and now im really used to hearing american accents but i cant pick up the british ones. I mean, they are so different not only in their rhythm but also in their specific sound. for instance, words are generally pronounced differently, like "jungle" and "but" or "one" . In all of these cases vowels are different and i can understand what they say only coz i can recognize words not because i recognize every single sound...wuts wrong?