Germany isn't entirely homogeneous, so there may be some regional pronunciation differences.
Germany wasn't unified into a single nation until the mid 19th Century. The ancestors of many Americans of Germanic heritage came to the US around or before that time, when regional differences would have been greater.
My Dad's family is Germanic, but they came by a different route. Around the beginning of the 19th Century his ancestors left SW Germany for southern Russia. They were "Volga Germans", invited to bring modern farming techniques and settle a sparsely populated part of Russia. Fast-forwarding to the start of the 20th Century, and my Grandparents saw what was about to happen, knew German farmers would not fare well, and came to the US. My Dad was born here, but his first language was German. I don't know whether it's regional, Russification, or Anglicization, but I'm pretty sure my family name would be pronounced differently in Tuttlingen - where many of my family name live - than how I learned it growing up.