Be careful! In USA there are the "South" and "North" pronunciation. I've lived in USA for a year in 2015 and I can definitely say to you that South pronunciation is difficult to understand. Also, there is a difference between "white" and "black" pronunciation (don't ask me why!), so, you will find plenty different accents. My advice, just watch some American series or movies and COMPARE their pronunciation. My pronunciation is a mix of Brazilian, Southern and Korean English! hahhahaha