[catalogia]

There were American companies inclined towards blacklisting German Americans at least. FDR made it illegal for them to do that with Executive Order 8802, probably because German Americans were such a large portion of the population that blacklisting them (let alone interning them) would have threatened the war effort.

https://en.wikipedia.org/wiki/Executive_Order_8802

Note that in Hawaii, Japanese-Americans were a significant portion of the local population, about one-third. Of the 150k+ Japanese-Americans living in Hawaii, only 1,200 to 1,800, or about 1%, were interned. On the mainland US where they were a smaller portion of the population, far more Japanese Americans were interned. This discrepancy probably comes down to a matter of practicality again; one third of the population is just too many to intern.