It would be bad to say Western engagement "directly caused" the fall, as it's not like they marched an army into Edo and dismantled the government. At the same time, contact with the west caused the sonnō jōi movement, which was instrumental to the fall of the Bakufu. The Mito School already set the background that the emperor was to be "revered", but without westerners there would be no "barbarians" to expel. Likewise, the attitude towards whether or not to open the country, as well as the wish of Satsuma and other clans of restructuring the government in order to respond to external threats happened because...there was a (perceived) external threat. Things like natural famines or earthquakes or existing socioeconomic inequalities can't be blamed on the west, but the opening of trade with the west surely disrupted many internal relationship networks (just like in China!). The Bakufu was unlucky to run into a string of quick successions in a row, and that can't be blamed on the west, but surely the Cholera epidemics can be partly blamed on the increase in foreign trade. I don't think anyone could successfully argue that the West was the only cause of the fall of the Bakufu, but at the same time I also don't think anyone could successfully argue that the West was not a strong contributor to the fall of the Bakufu. This is my stance on China, too.

I am not actually well-versed in the historiography of the Bakufu. Maybe /u/NientedeNada have more input? One change I do know is that in the pre-war era, the historiography (inside Japan at least) painted the Bakufu and the Edo period in general as oppressive, backwards, and everyone but useless and corrupt government suffered. In the post-war, the trend seem to have moved to towards saying that the Edo period, even the late period, especially when compared to Imperial Japan, wasn't all half bad, and the the Bakufu was very powerful, centralized, and well-functioning, and really did as well as they could given the incredibly bad hand dealt to them.