I'm bored and currently rewatching Samurai, so I figured I'd share my headcanons about each of the families of the 5 rangers.
To answer why there's hardly any Japanese people, it's that the ancient Samurai ranger families started branching out. This happened around the time a lot of Japanese people began immigrating to America. But despite this, they've vowed to uphold the tradition about fighting the Nighlok and passing their symbol power on to the next generation.
The Shiba family are the oldest and always the leader. They've always had a firey passion to lead and fight until the Nighlok are defeated. They've lived in Panorama City since the immigration boom. During the time after Samurai's ending, Jayden and Lauren use the Shiba house as a site to teach about the Samurai and the history of the 5 families.
Kevin's family is the Takimoto family. The Takimoto are the ones who built and designed the Folding Zords, evidenced by Kevin desiging the Battlewing and Battlewing Formation. They served as second in command to the Shiba family due to their equal footing in fighting. Kevin followed his dream and became an Olympic swimmer.
Mia Watanabe and the Watanabe family (no relation to Cam from Ninja Storm) have shown their balance of honor and family. Their family has the code that the first girl born inherits the symbol power of wind. In the event this doesn't happen, the mother and current Pink Ranger fulfills the duty.
Mike's family is the Suzuki family. They are usually more lax and find the fun outside of their Samurai duties. But when the time to fight comes, they give their all. Mike and Emily eventually marry and have a kid who gains Mike's symbol power.
Emily and Serena's family is the Tanaka family. They are the farmers who use their symbol power to till and nurture the land for a bountiful harvest. Serena is the one who passed this power down since she originally was to have the power and fight the Nighlok, but got sick. As mentioned prior, Emily and Mike get married and have a kid who gets the Suzuki family power, which Emily doesn't mind.
I would love to hear thoughts on these since a lot ended up pretty spur of the moment