What is the current reality of Christianity in China and how has this been shaped by the legacy of Western imperialism?

The reality today is that the Chinese Communist government deeply distrusts the role of Christianity in Chinese culture. To the ruling elites, this unease regarding Christianity began when Western imperialism reached Chinese shores in the nineteenth century.
Then, the first missionaries to China were immensely successful in converting many of the local population to the foreign religion. Things continued unchanged until the Communist revolution and subsequent elevation of Mao Zedong to the chairmanship of the People's Republic of China in 1949. Mao championed an anti-imperialist platform and successfully purged all presence of foreign missionaries from China by 1951. Left undefended were hundreds of thousands of new Chinese Christian converts, now the target of Mao's Communist Party.
As a result of persecution, Chinese Protestants became compelled to declare their allegiance to the state and to disavow any connections to Western imperialist powers. For its part, Mao's Communist Party decided to tolerate Christianity within its shores, so long as all churches came under the auspices (and jurisdiction) of the state.
Pressured on all fronts by the Communist regime, the Church of Christ (CCC) in China eventually signed a manifesto declaring a sundering of ties to Western churches. In the manifesto, the CCC affirmed its loyalty to the state. By 1954, the CCC openly called on all Chinese Christians to abide by the dictates of the Communist Party.
From the 1960s to the 1970s, the Cultural Revolution swept the country. Chinese Christians were brutally persecuted, and many died. As a result, underground churches flourished overnight. Today, the Chinese Communist Party tolerates Christianity, but only if its churches submit to its dictates. All churches that are formally registered enjoy a surprising degree of autonomy. Underground churches, however, continue to experience severe persecution.
This is because the Communist government continues to view Christianity as a subversive influence and a tool of Western imperialism. As such, it retains strict control over how Christians worship in any of the state-approved churches. Meanwhile, the leaders and members of underground churches are often interrogated, imprisoned, or tortured. Last year, the Chinese government increased its targeting of underground churches. According to the South China Morning Post, Xi Jinping's administration increased already burdensome fines on anyone caught facilitating underground church activities.
The New York Times documents the destruction of churches by the Communist government. Again, the Chinese state apparatus is invested in suppressing what it fears it cannot control. For more, please refer to the links provided.
For more about how western imperialism has shaped the current reality of Christianity in the country, you will want to explore what is called the Unequal Treaties of China.
This set of treaties was negotiated between China and several Western nations during the late nineteenth and early twentieth centuries. One of the first of the "unequal treaties" was the treaty of Nanjing, negotiated after the first Opium War. This famous treaty was the one which made Hong Kong a protectorate of the British. Hong Kong returned to Chinese sovereignty in 1997.
Also, four new ports (Ningpo, Shanghai, Amoy, and Foochowfoo) were opened up to the British. Until the treaty, the British could only trade at Canton. For more on the unequal treaties, please refer to the link below. Because of these treaties, the Chinese government developed an abiding suspicion of all values it considered foreign to the Chinese culture. The suspicion continues today and explains why the practice of Christianity is severely curtailed and monitored by the communist state.
https://www.britannica.com/biography/Mao-Zedong

https://www.britannica.com/event/Unequal-Treaty

https://www.chinacenter.net/2016/china_currents/15-1/protestant-christianity-in-the-peoples-republic/