It isn't that hard to find out if a particular person came to the States during those years; I can do it in several ways. If you have the name, age and gender of the person, I could try and do some checking online for you and tell you what I find. If I find nothing, I could provide other resources for you to follow up on, on your own.
There was no restriction, other than the normal numerical quota already in place at that time, for Japanese citizens that I can find. It wasn't until February of 1942, with the Act of Congress authorizing internment of Japanese and Japanese-Americans on US soil that this was done officially. And prior to August 8, 1941 when the US declared it, we were not yet at war with Japan.