About as much as you influence your parent's decision, however minorly or majorly.
The Soviet Union did and as a direct result, the US did as well.
Yes
Korea
japanese
South Korea
North Korea has issues with the US. But the US does not hate Korea. The US has a strong and very old alliance with China that makes then stronger than Korea.
The attacks by North Korea on South Korea were seen as a proxy effort by China and the USSR to extend the influence of communist states. The US was pursuing a policy of containment to limit this spread. When the UN condemned the invasion, the US and other UN members sent forces to assist the South. Eventually this led to a prolonged war (1950-1953) between forces of the US and China in Korea. -- Under the "domino theory" any spread of communist influence, as in Korea, could lead to the loss of Japan or other Asian countries. The US saw the North Korean offensive as a move to expand Soviet influence, and acted in order to forestall aggression elsewhere in the world. The criticism of Truman as being 'too soft' on Communism after the fall of China gave political impetus to US involvement as well. A similar scenario led to the massive US intervention in Vietnam in the 1960s.
South Korea
No. The US leads the world in enforcing sanctions against North Korea.
C) north of the 38th parallel.
South Korea welcomed us, North Korea fought us.
Korea and the US are almost on the very opposite side of the earth.