A lot will depend on what region or even state a person id from. The people in the New Englsnd states speak very similar to the British English, but the further you get from the New England states the less it sounds like British English and the greater difficulty there is for the people to understand British English. A person from Southwest Texas can hardly understand somebody from Massachusetts It is almost justified to say that in North America we speak at least 50 different forms of English and the Canadians have quite a few variations also.
I suspect you would have difficulty in understanding the English spoken in Lafayette, Louisiana