How has a change of political party or a change in the level of stability in China and USA affected tourism?

Well, the political party of China really hasn't changed,
they are still a Communist nation, but what has changed is their economic policy. They
have embraced capitalism which is considered a "Western" form as opposed to Communism
that was in place when Mao was the leader of China. When the Tianamen Square riots
happened, it was clear that the Chinese government would not tolerate democracy but
because of the success of trading with the Western world has proven so beneficial
especially over the past 10-15 years, China has begun to see the benefits of welcoming
touriist since this is a capitaliist form of income as well. China has been more open to
welcoming English teachers because English is the international language of business.
China is very accepting of ESL teachers and of course, with the embrace of Western
trends, movies, along with China's own tourist attractions, that brings people to China.
 You need to remember that China needed to stabilize if they wanted to reap the benefits
of a stronger economic system. Obviously, they are now one of the stronger (not
strongest)  economic nations in the world.  Hope this helps!