I think there are two big reasons. First, the American accent is actually how English was spoken in England until the 1800's. What you have with American Engli

I think there are two big reasons. First, the American accent is actually how English was spoken in England until the 1800's. What you have with American English is the US retaining the older style of English while British English evolved differently. Now, with Netherlands, England and Netherland were very closely linked throughout the late 1600's and especially the early 1700's. They were both Protestant powers, fighting various wars against Louis XIV and his Catholic France. In addition, at one point, they even shared a leader, William of Orange who became King William of England in 1688. Later in the century, they diverged. Thus, you have the same phenomenon that you had with the United States, they both retain the old English pronunciation from the time when both were much closer to England. British English evolved differently, leaving both Dutch English and American English much closer to each other than British English.