This video, created by Youtuber Danzig HD Mapper, shows the changing political boundaries in what would become Germany and Austria, from the years 843 to 2018. This video includes many of the smaller states that made up the Holy Roman Empire, including the duchies of Saxony, Bavaria and Bohemia, and the Italian possessions of the Empire.
Youtube Ollie Bye has also created this video The Holy Roman Empire: Every State, Every Year, which offers an even more in-depth look at its borders between the years 843 and 1871
Khey Pard also offers a year by year map of Germany and Austria, starting in 843. While it is a little less detailed than the others, it shows all of Europe, offering the viewer a better understanding of the Empire’s territory in Italy.