Here is a great way to work on improving your American accent:
Buy a book on audio. I suggest a non-fiction topic because the speech is generally better suited for this type of practice.
Listen to a sentence or a phrase, then pause it and repeat what the speaker said. At the same time, record this so that you can listen back and compare how you sound versus the speaker on the audio. Keep in mind that this is not a memory test. If you don’t remember things word for word once in a while, just keep going. Some phrases will be longer than others.
It’s a good idea to also have the hard copy of the book so that you can sometimes just play it while reading the text. This is especially valuable if you read the text first, only a few pages for example, and underline the difficult or new words. That way you can later pay close attention to how these words sound in context. Also try to listen to the intonation and word stress. Do this often. It will help you a lot!
I DON”T recommend Amazon’s product, Kindle, which seems to be a computer generated voice and not an actual human reading. The speech sounds artificial without any rhythm nor melody.