We did place the Japanese and some Germans and Italians in concentration camps. However, we had no death camps -- no intention of committing genocide -- and the conditions in our camps were vastly better than those in Nazi camps.
That is not to say that our concentration camps were fair to those people who were sent to them; they were not. However, the difference in degree of error was vast. We responded to the declaration of war against certain countries, and their declarations against us. We did not start rounding up the Japanese or anyone else or persecuting them before war existed, as the Nazis did to the Jews; and, of course, there was no "state of war" between Germany and Jews, since the Jews didn't even have a country but thought they were citizens of various countries in Europe, including Germany.
The Nazis, of course, didn't see it that way.
By the way, the concept of a "concentration camp" was more or less invented by the British during the Boer War in South Africa, though there had been some earlier examples. See below: