People don't leave China to any considerable extent. 200.000 Vietnamese refuges came to China 1979-1981.
We aid China
Japan left Vietnam because the US won the Vietnam War. The US effectively kicked them out of the area. This was preventing China from invading Vietnam as well.
2001
on a plane
China is a great business partner.
No it is summer in China as well as both the US and China are in the northern hemisphere.
The US has a trade deficit with China. That means China sends the US goods worth worth more money than those the US sends China.
China is smaller than the US by about 257,000 km2
Because the US is trying to overpower China
If you stretch The Great Wall of China to make it straight, it is longer than the USA. If you leave it like it is now, it isn't longer.
Without widening the war into other countries (Laos and Cambodia), and risking war with either Red China or the Soviet Union (Red China entered the Korean War), the war was un-winnable. US fighting forces pulled out in April 1973. ALL US PERSONNEL were out by April 1975.