I come from Xi 'an. I went to visit relatives in the United States and made an appointment with Chengdu. What is the reason?

The US Embassy has five visa offices in China: Beijing, Shanghai, Chengdu, Guangzhou and Shenyang. For non-immigrant visas, the visa location is determined by the place of residence. For example: Beijing, Tianjin, Xinjiang, Qinghai, Gansu, Shaanxi, Shanxi, Inner Mongolia, Ningxia, Hebei, Henan, Shandong, Hubei, Hunan or Jiangxi-Beijing, the visa office of the American Embassy.

Guizhou, Sichuan, Yunnan, Tibet or Chongqing-US Consulate General in Chengdu

Liaoning, Jilin or Heilongjiang-US Consulate General in Shenyang

Shanghai, Zhejiang, Jiangsu or Anhui-US Consulate General in Shanghai

Fujian, Guangdong, Hainan or Guangxi-US Consulate General in Guangzhou

But now American visas can be used at any American consulate. According to your situation, Beijing should be the most convenient. And according to experience, Beijing is the most efficient. It doesn't matter what your household registration is, it's mainly to choose your own convenient consulate and then make an appointment according to the location.