At that time, the United States was tolerant of even illegal immigrants including some Japanese working for illegal sectors, and didn't send back those who have already opened the golden door.
The identity of the United States is to be multi-ethnic and multi-cultural, and it's itself one side of American culture.
It was a good and innocent time.
I wonder why some angry and stupid conservative Americans and Japanese have a tendency of excluding foreigners and don't want to get back the wonderful days.