Part question, part idle wondering is the source of this thread.
Why was small independent citystate republics so prevelent in northern Italy, which 'at best' paid lip service to HRE, if they weren't completely ignoring any thought of having some liege over them, and half-indepedent states in Germany (republics, archbishopies and tiny city-sized duchies such as Luxenbourg alike), under the de jure leadership of the Emperor), while nearly non-existing in the rest of Europe?
How to make this even more prevelent in the rest of europe, with similar city states in France and Netherlands and the like, and what changes would this cause to the European history in terms of expansion and 'internal' warring?