@ /u/RecentArtichoke

You may want to take a look at this answer + back and forth, found from the FAQ. To supplement this with some other specifics, see this comment (/u/diana_mn), as well as this one for another outline (/u/churakaagii) on the events that led to the collapse of the Shogunate.

Assuming you have read through/have finished reading through these, and are looking for good English resources - you'll be hard pressed to find (as far as I'm aware) a definitive explanation of what really was the cause (beyond super broad generalisations - they met Western people), just because there are so many contributing factors and entities responsible or involved in the transition into modern Japan. You may want to have a look at books which deal with the Meiji restoration as well - book list recommendations here because off the top of my head I can't think of anything better. Jansen's The Making of Modern Japan also does go into this a bit, and maybe you'd like to see what resources he uses for further research into this topic.