As far as I understand, the profession is not exactly the same here as it is there. Therefore, education in optometry there wouldn't transfer to the US, and vice versa. If you intend to live and work here as a US optometrist, you better go to school here. If you want to live and work in Germany, look into what "optometry" there entails. I believe it's more like what optometric technicians here are, but if you choose that, you probably want to get one of their degrees over there. Good luck!
(my family is actually from Germany, and when I try to explain to them what optometry is, they're baffled that I'm spending so much time, education, and money going into the field-- because they think I'm referring to optometric technicians/ opticians. Over there, they mostly have that and ophthalmologists, less of the in between primary care that is optometry. This is my understanding anyway, I hope that made some sense!)