It's understandble in Hawaii

There are many person who do practice Ken-doh in Hawaii, USA.
Ken-yu-kai, a name of Ken-doh club has practice at Kenshikan-DoJo in Honolulu.

I can see why Ken-doh had expanded in Hawaii. The reason why was for immigration first 20th  century.
Japan had needed to expand their labors out of county for population explosions inside.
So many people went to foreign countries, for example, North China, East Russia, Brazil, Hawaii, etc.

Hawaii Ken-doh Federation History

  

http://www.hawaiikendo.com/history.html

According to their explanation of Federarion History....
 

The first government-contract immigrants to Hawaii from Japan arrived in 1868, the first year of Meiji Era right after the end of Tokugawa Shogunate's reign.

They brought with them the art of Ken-doh and Su-moh to the islands. The Ken-doists at the time were actual Samurai or students of Samurai instructors, so their technique was more of thrusting and cutting with a real Japanese sword, Katana.

In 1885, the immigrants were reported to have demonstrated these arts for King David Kalakaua. A year after the Sino-Japanese War in 1895, a Ken-doh match was reported to be held on Oahu.

 In 1915, an official Ken-doh instructor for the immigrants came to Hawaii for the first time. Ken-doh became part of the requisite grade school curriculum in Japan in 1911 to help children develop physically and morally.

By 1940, when the Hawaii branch of Dainippon Butoku-Kai (the organization of Ken-doists in Japan) opened, Ken-doh was taught at the many Japanese schools and Do-jo throughout the State.

Ken-doh was banned in Hawaii in1941 at the onset of World War II, but Mikami Do-jo re-opened in Kapahulu soon after the war.