After having been driving recently in the US and Canada I suppose you will find roads narrow. Maybe not motorways but local roads are definetely narrower in Europe. And if you drive in areas around the mountains expect to find tiny winding roads. In Canada, in Jasper National Park, we have seen mountain roads that in parts of Italy or Austrian Alps would be considered as motorways. Usually this roads are the most beutfiful or take you to beutiful places. In Austria and through the Black Forest you will travel on them a lot because motorways are not very extended.

In Germany, as pointed in some messages, pay attention to your rear mirror.

Parking in German cities is not easy and you have to understand all those signs that limit the area to only neighbours.