On the contrary, I am intimately familiar with every legitimate Christian community which has operated in Asia since the time of the early church. I am also familiar with those heretical groups such as the Paulicans of Armenia, and also with the persecuted crypto-Christians of Japan, who unfortunately were not fully catechized before the Portuguese missionaries were executed, and with numerous other groups. However, the denominations which I enumerated, which include the Christians you mention in China and Iran and India
The church in China was a part of the Assyrian Church of the East, which is sometimes inaccurately called the Nestorian Church (it does venerate Nestorius, and for a brief period in the 5th century it adhered to his deeply flawed Christology, but in the early sixth century this was replaced by the Chalcedonian-equivalent Christology of Mar Babai the Great), but unfortunately its members in China, Mongolia, Tibet, Central Asia and Yemen (where it reached its southern-most point in the island of Socotra) were killed off by Tamerlane and his sons starting in the 12th century, in a sweeping genocide, which left only the portions of the Church that existed in Iraq and Iran (where it still thrives), and among the Mar Thoma Christians in India. The Mar Thoma Christians, as the name implies, were first evangelized by the Holy Apostle Thomas, who was martyred in Kerala in 53, AD, and I have written about them numerous times on the forum, including about their relationship to the Kochin Jews of Kerala, and also other places evangelized by St. Thomas, with his disciples Saints Addai and Mari, such as Edessa.
In both places, the Church of the East coexisted, and continues to coexist, with Miaphysite communities (which is why the Mar Thoma Christians who resisted integration into the Syro-Malabar Catholic Church reached out to the Patriarch of Antioch and not the Catholicos of the East, although the Syriac Orthodox did transition them over to the West Syriac liturgy as used by the Syriac Orthodox in Iraq, Syria, Turkey, the Holy Land and elsewhere.
However, later, what is now the Assyrian Church of the East and the Ancient Church of the East were able to convert members of the Syro Malabar Catholic Church (which used a modified form of the East Syriac Rite). Indeed it was an Indian bishop of the Church of the East responsible for the end of the uncanonical hereditary patriarchate that had plagued the Assyrian church for centuries, who caused this by forming the traditionalist Ancient Church of the East jurisdiction when the last hereditary Catholicos, Mar Shimun XXIII made an ill-advised change to the liturgical calendar, and installing Mar Addai II, memory eternal, as its Catholicos. Later, Mar Shimun XXIII was unfortunately the victim of an assassination in the 1970s, and his successor Mar Dinkha IV, memory eternal, began a reform program in the Assyrian Church of the East which aimed to restore traditions to that church which had been suppressed and at the same time to reassure the larger Christian community that the Assyrians were not Nestorians. This was a success, and it also facilitated the beginning of the reunification process between the Assyrian Church of the East and the Ancient Church of the East, which started around 2010, and probably would have been finished already had it not been for the ISIL war in Iraq which had a profoundly adverse affect on the operations of the Church in much of its ancestral homeland, and also the deaths of Mar Dinkha IV and Mar Addai II.
Many heterodox Christians, unaware that the Church of the East is still intact and operating in Iraq, Iran and India, attempt to ascribe various false beliefs to it (this is also commonly done with the Ethiopian Tewahedo Orthodox Church). For example, I have seen it argued that these churches are, or were, Sabbatarian, or that they adhered to various doctrines that are widely believed in by Restorationist Christians or by some Evangelicals such as Baptists, when in reality we know this not to be the case, because the history of the Church of the East, and also the Syriac Orthodox Church, which has always heavily overlapped it geographically (in part because the two churches serve the same ethnic group, since many Syriac Orthodox, particularly in Iraq, identify as Assyrian, and the Classical Syriac language and the Peshitta translation of the Bible binds these communities together), is extremely well documented, including its historic liturgies, and related facts.
Indeed we even have (most of ) a book of doctrinal theology from the Paulicans, who were heretics, who lived in Armenia and some of whom emigrated to Romania, but all of whom converted to Orthodoxy in the 19th century. This did not stop the Landmark Baptists and other groups from including the Paulicans among their alleged predecessors.