I guess I'm curious what you mean by 'western academia.' I teach undergraduate level intro World History survey courses every semester and I can assure you both of those are covered.

In fact we will be covering the Three Kingdoms next week! Right on schedule after the second midterm.

The Taiping Rebellion is usually taught within a unit comprising the Opium Wars and foreign interference/influence in China or the changing relationship between Europe/China - after all the Western powers generally sided with the Qing.

*Editing to add- that the conflicts aren't included just for being 'big' or 'deadly'- those in and of themselves aren't really reasons to include a particular war or battle in a survey course. Instead, they are included for how they tap into, connect with, or illustrate broader currents in World History.