sharke
I'm a Geordie from the North East of England and I have real problems being understood in New York sometimes, even after having toned down my accent considerably since the 10 years I've been here. This, in a city which is a cultural melting pot. You'd think people would be attuned to every kind of dialect here but no. I have to say "small decaf" 3 times before they understand me in Starbucks.
Once a guy asked me if I was Eastern European, he refused to believe I was speaking with an English accent. Mind the Geordie dialect is pretty thick.
That's interesting and a bit surprising. I'm also from the north east of England and have never had any problems being understood by people from any part of the US. And when we've had American visitors over here they even get the gist when we really lay it on thick for a laugh.
Some figures of speech can be confusing (rather than the actual accent), for example your last sentence ('mind' for 'then again') is a bit of a northeastern thing.