system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If both sides spoke British-English during the Revolutionary War, how did America slowly develop their own dialect?

I understand how in modern times, say if an Englishman came to the US and lived there for a lengthy period of time, their accent would slowly disappear, but that is due to the fact that they are constantly hearing the American dialect being spoken wherever they go, right? If that is the case, I doubt that the original colonists went out of their way to 'develop' their own dialect out of spite? Perhaps I am overlooking something obvious here, but I just can't think of it. Thank you!
gpt
Both the American and British English variants are different from what they were at the time of the Revolution and both have different parts that are closer to the English spoken then. For example, the way that Americans pronounce "Rs" is closer to how English was spoken then. 

Both dialects have drifted over time (with the British very recently taking up the received pronunciation after the adoption of the radio and tv). American English on the other hand was heavily influenced by German immigrants, and to a lesser degree the languages other immigrants have spoken.