Why is British English accent different than American English Accent?

I think accents envolved with time, and this may start after1776.

According to what i did read the British accent itself is not the same, they have varity, in same time American accent also diffrent from region to another in United state specially since The structure of American society consisting of different ethnicities.

When did Americans stop talking british??? that happened in mid of18th.

Why Do Americans and Brits Have Different Accents?

When did Americans Stop “Talking British?”