Asians who immigrated to the United States after marrying American service personnel primarily came from

Asians who immigrated to the United States after marrying American service personnel primarily came from Korea.

Explanation:

Most of the Asian immigrants who acquired citizenship by marriage and came to the United States came from Korea. This was so because during the Korean War, in which American soldiers participated during the 3 years of the conflict, the American forces were in close contact with the local population. Thus, the inhabitants of South Korea saw in the allied forces the protectors who were defending them from the tyranny from China and its North Korean ally. This generated a constant social and cultural exchange, which in many cases resulted in loving relationships between American soldiers and local women.

In turn, this situation occurred to a much lesser extent in Vietnam, because in that conflict the local population saw the Americans as a threat and an aggressor power, with which said exchange did not take place in the same proportion.