There is no motivation for US to interfere with problems in Hong Kong. US knows that everytime they promoted democratic movement in Middle-Eastern countries, the results became chaotic status like simultaneous eruption of terrorist groups. So, the US wouldn't like to repeat the same history. And, China's liberation party is expected to be much stronger than armies of Middle-Eastern dictators. It is too dangerous for the United States to attack China's army. What is needed for protesters in Hong Kong is to show benefits for US to support Hong Kong.