Why are Vietnamese so right wing in the US? They tend to be NDP supporters here... and by here, I mean in Ottawa.
Anti-communism. That used to win among Chinese-Americans and Korean-Americans... but China seems more a trade partner to most Asian-American groups than the old source of anti-capitalist extremism. Korean-Americans are still hostile to Communism... but only toward the Communism in North Korea. Truth be told, Korean-Americans would probably be delighted to find that the People's Liberation Army were liberating North Korea after the North Korean regime did something incredibly unwise.
Many Vietnamese-Americans have more recent and bitter memories of the Communist takeover of Vietnam and personal consequences. Koreans who have personal memories of the Korean War, let alone Chinese who remember the Mao takeover, are now old.