They were born here. Or, a smaller number of them were born in British owned Hawaii ~ they burned into citizens as if by magic the day we annexed the Islands.
Back when I researched this subject in depth I was surprised to learn that only Japanese aliens were interned during WWII. It was they who were offered the option of repatriation. Thousands opted for it.
American citizens of Japanese ethnicity were "asked" to move away from the West Coast, and if they could not find a place to go they were housed in "relocation camps" from which they could come and go at will.
I also know many on-line sources do not acknowledge the distinctions between internment and repatriation.