There is no XL N14644 model. There ARE North American XL 325, 330, 335, 340 and 350 models (though a 350 is a newer model).
When you tap on the satellite bars, and then tap on the version number, what does it show at the top of the next screen as being the model?
If you have a European map that covers Germany and have installed the map on the computer, it'll work.
The usb connection is to connect your unit to the computer. When you start Home, Tomtom's computer software and the unit is connected, updates get sent to the unit via the supplied usb cable. You can also charge the unit via the connected cable.