Kusatsu began acting in Honolulu summer stock, and after studying theater at Northwestern University, started to make his mark on the small screen in the mid-1970s. Usually mustachioed, with a dapper, professional air, he has most often played doctors, but his repertoire has included a generous sampling of teachers (usually college professors), businessmen, detectives, church ministers and other intelligent, middle-class types. With his quiet, wry line delivery, Kusatsu made a memorably clever and hilarious sparring partner for Archie Bunker (Carroll O'Connor) on several episodes of All in the Family as the Reverend Chong, refusing to baptize Archie's grandson without the permission of the boy's parents.

Kusatsu was subsequently a regular on several series, but neither the adventure Bring 'Em Back Alive (1982–83) nor the Hawaiian-set medical drama Island Son (1989–90) (in which he played one of Richard Chamberlain's colleagues) lasted very long. His many TV movies have included Farewell to Manzanar (1976), a story of the internment of Japanese Americans during World War II{he also guest starred on an episode of Lou Grant on Japanese American internment camp}; Golden Land (1988), a Hollywood-set drama based on a William Faulkner story; and the AIDS drama And the Band Played On (1993). He appeared in four M*A*S*H episodes and later starred in the short-lived ABC series All-American Girl (1994–95), the first Asian American family sitcom.

Feature roles, beginning with Midway (1976), have generally been small, but Kusatsu was especially busy in the '90s with roles in Dragon: The Bruce Lee Story (1993, as a history teacher) and In the Line of Fire (1993, as a Secret Service agent). He also appeared as an high school English teacher in American Pie (1999).

Kusatsu is married to Gayle Kusatsu; they have two sons, Kevin and Andrew.