As you probably know, in the states there are many accents - not only one. We have diffrent accents depending on the geographical region we were raised in. It’s because of its size and well it’s the same everywhere not just the US. The bigger the distance the more different the language and accent is. The languages and accents naturally evolve and change becoming really different over time that’s why we have schools to prevent that. Slang is the result of evolution that’s how new languages are made. It helps speed up the flow of words.
Usually accent is inherited from your parents as a baby you mimic the words and try to get it as close as u can then u end up talking like them, but like all it can change.
How many different accents are there in the USA?
Southeastern - Mixed north and south (Fl, Ga, Al...)
South - Y'all (TX, LA...)
North - (IL, MD)
New York
New England
Southwestern
Mountain
People say you talk funny whan you travel to a new region =]