I am only aware of one US rocket that used hot-staging for maintaining proper ullage during stage seperation--the Titan family. Otherwise, US rockets tend to use reaction control systems or small solid ullage motors to settle fuel. However, Soviet rockets & their derivatives (Russian, Indian, Chinese...) have been hot-staging since the very first Soviet upper stage (as should be apparent from the open interstage surrounding the Blok-E RD-0105 engine).
Why did this practice persist? Conversely, why did US rocket manufacturers never adopt the practice?