I had problems communicating when I moved from the west coast to the east coast.
There were many memorable times when someone spoke to me and I either couldn't understand the accent, or I didn't understand the local slang. As someone else mentioned, only the less educated were completely incomprehensible to me. Sometimes when people spoke, it sounded like a record playing at the wrong speed, decipherable, but it took conscious effort to comprehend what they were saying. It went the other way, too. Sometimes I could understand them, but they could not understand me. It took me years before I could imitate the local accent accurately, and I feel like many people considered me an outsider until I could!