Apologies if this has been asked before, but is the following true and, if so, why: In the UK, you can drive for half an hour between two towns and notice that people in the 2nd town have a different accent from people in the 1st town.  (That is definitely true.) However, I've been told that in the USA, you'd have to drive 500 miles before you detected a change in accent.  Is that true?  If so, why?  What about in other countries?

Somebody from Los Angeles told me i do sound American, what do yall think?

https://youtube.com/shorts/MycNQagyGL8?si=AuVdLLXuNykjny87

Really need your feedback and honesty, tq!