Seeing that Japan was economically devastated by the war, why didn't more civilians move to the United States?
Edit: thanks for the responses! They really helped me understand why there was a sudden reduction of *emigrants during this time period. I was interviewing a Japanese American (for a school paper) Kibei who moved back to America in 1947 after the war and was wondering why so little Japanese decided to do the same.
Until 1952, Japanese civilians literally couldn't actually immigrate to the United States. In 1945, the Immigration Act of 1924 was still in effect, which barred Asian immigration. As such, there was no way for Japanese civilians to immigrate to the United States immediately after World War 2, even if they wanted to.
The Immigration Act of 1952 ended the policy of Asian exclusion. Even so, it was rather heavily limited, as it only allowed 100 visas to go to anyone with at least one parent of Asian descent, even if they were immigrating from, say, France.
The long and the short of it was that there were substantial limitations on Japanese movement out of the home islands in the immediate aftermath of the war. Although Truman had liberalized US immigration law for refugees from Europe in December 1945, such liberalization did not extend to immigration from East Asia. although the wartime alliance with the KMT had led to the repeal of the anti-Chinese laws and the Luce-Celler Act of 1946 allowed for Indian and Filipino immigration, many of the strictures of the Immigration Act of 1924 remained in force. This law made it quite difficult for Japanese and other non-whites to enter the US as there was a complex system of national quotas. Nor was the American-led occupation force of Japan (SCAP) eager to allow for Japanese to leave the home islands. SCAP officials viewed the few Japanese voices calling for a more liberal US immigration policy as legacy of Japanese imperialism. The logic behind SCAP's hostility to Japanese migration, which also cloaked a good deal of racism, was that the their reconstitution postwar would represent a return to the various prewar Japanese colonization societies that were connected to the Japanese nationalist extremism. SCAP openly discouraged postwar Japanese immigration associations and tightly controlled all Japanese movement outside of the home islands.
By the time that American immigration law had significantly liberalized in 1952, the Japanese economy was well on the road to its postwar recovery. It thus became a moot issue.
Legal reasons aside, why would someone want to migrate to the country its been at war against?