Definitely incredibly influential, but I would say that Roland, KORG, Yamaha, etc. are matched by the likes of Moog, Sequential, Oberheim, Access, and many others (from E-mu to Linn to modern Eurorack) on the hardware side, and on the software side by DAWs such as Reason, Live, FL Studio, Logic and myriad plugins. Definitely a fair amount of US and Europe as well as Japan.