No, it was because there was a specific risk of an invasion of the west coast and a large native population of Japanese Americans lived in that locale. There wasn't the same situation on the east coast and Germany/Italy were not the threat to the homeland.
It was a specific request from Western Defence Command directly because of the risk of a large subversive element and the sincere belief that an invasion was possible.
While there wasn't a direct thread to the homeland, there was a significant (if not arguably a greater risk) of subterfuge on the east coast and within industry.
You also have acts of sabotage on the eastern coast by the Germans as early as '42, with also the U-Boats sinking numerous ships within or near US waters.
Yet, two other members of the Tripartite Pact did not receive the same treatment - in fact, no where near. There are also a few other questionable parts:
Why did Hawaii, closer to Japan and at a significantly greater risk of invasion, have a significantly lower rate of internment than on the mainland? Hmmm...
Why did it take three years for internment to be rescinded even though the risk of invasion had passed by June '42 after the Btl. of Coral Sea and Midway?
The United States labelled a huge group of people as a threat simply because of their ethnicity, whereas other ethnic groups were treated completely differently.
There's a word which beings with R, and that's the main reason.