How did Japonism, if at all, affect manga/anime? While researching my own question How important was the invention of blue towards anime?, I landed relatively quickly on Hokusai, which was one of the key instigators of Japonisme.


  Japonisme, is the study of Japanese art and artistic talent. Japonisme affected fine arts, sculpture, architecture, performing arts and decorative arts throughout Western culture


Although Japonisme mainly influenced the European art, it also had an effect on the Japanese art scene. 

So did Japonisme also lead to, or influence the creation of manga/anime as we know it nowadays?
Short answer is no. Beyond making the world aware of the early, pre-war concept of manga, there is little to nothing to do with modern post-war manga. The influences are just a footnote in history in terms of European art movements. 

Post-war manga we know as manga today is starkly different from  the prototypical  manga of the type, such a the compiled work of Hokusa Manga.