Will I be harshly judged in UK?

I just want to let it be known that not all americans are redneck fatties that are patriotic and mean,most people in America make fun of them I live in the midwest and we think they are all hillbillies! Which is still prejudging them because they are not all like that. But I'm afraid that when I go to UK in a year that I will be prejudged for being American. I am educated, and don't look at me different please I would like to experience your culture. Another question, can you tell the difference between midwest,boston and southern American accents they are VERY different and Americans can only tell the difference between two British accents sorry I knows theres more any thoughts?