There are different accents in the US. Talk to people from Texas, Louisiana, Rhode Island, and California, they all sound different with the person from Louisiana probably being the most incomprehensible.
For that matter talk to someone from Dallas, TX and then someone from Tulsa, OK. That's only a 4 1/2 hour drive. They will both sound different. I'm pretty sure there's a different accent in Oklahoma City compared to Tulsa, and a different one in San Antonio compared to Dallas.