Executive Order 9066 was signed on February 19, 1942, approximately two months after the Japanese bombed Pearl Harbor and the United States entered World War II. The order provided that citizens could be banned from a hue swath of land on the west coast of the United States, and that citizens removed from their homes on the coasts could be interned in camps. If you look at a map, you will see that the west coast of the United States was the coast exposed to Japan, but certainly not to the other nations who fought with Japan, for example, Germany or Italy. So, one might reasonably question why the east coast of the United States was not subject to the same action, being at least as vulnerable to our European enemies.
While the United States government did round up some Italian-Americans and some German-Americans, most of the people who were rounded up and placed in camps were Americans of Japanese descent. Why? Some people felt (and feel) that because the Japanese had attacked United States territory already, they represented a greater threat to us. But the Japanese were a different race, and many people feel that the property seizures and internment were motivated by prejudice.
The lives of the Japanese people who were interned were ruined. They lost homes, land, personal property, and their sense of community and security. They were law-abiding citizens who voted and paid taxes. Two attempts were made to challenge the government's actions in court, but in both cases, the court ruled for the government. It was not until many years later that the government took steps to compensate these people (or their descendants) for the damage that had been done, in 1968.
I would like to think that the effect this had on our country was that we learned to not make military decisions motivated by racism or any other kind of "ism," but I am not completely convinced that we have learned this lesson because I am sure that many innocent people of Islamic and Arabic origin have suffered since 9/11.