/u/kieslowskifan has done a great job going over much of the information about the internment of German and Italians in this previous answer which I'd recommend checking out, but I would simply note that of the roughly 127,000 Japanese-Americans in the country, 120,000 were forced into these camps, 78,000 of whom were born in the United States. Compare this to the internment of persons for their German connections, which numbered 10,905. Hardly a number to scoff at, but consider that Americans of mostly or entirely German ancestry numbered as high as 25 million, and even if we winnow that down to households which were strongly German in culture, we're speaking of a million or more. Internees of German ethnicity were specifically targeted for their foreign extraction, or connections with groups such as the German-American Bund, and while there is much to criticize about the specific of the process, with hearings that could often seem like little more than a kangaroo court, it is not at all comparable to the broad-stroke process by which Japanese American's were interned.

Beyond Kies' answer, I'd point you to Undue Process by Krammer for a much more in-depth treatment of the topic.