Jiang in this sentence is a popular online expression, which means "China is a political legend who has never appeared in public, but holds power and serves as the mayor of several cities at the same time".
For example: Wuhan Yangtze River Bridge, Nanjing Yangtze River Bridge, Shanghai Yangtze River Bridge, Anhui Yangtze River Bridge, Jiujiang Yangtze River and so on.
When often read as Zhang, this bridge can be regarded as Wuhan Mayor: Jiangqiao, Nanjing Mayor: Jiangqiao, and Anhui Governor: Jiangqiao.