Assuming Keraite maintain Nestorianism /Christianity in its governance and didnt convert to other religions later on, influence on Nestorianism could be huge.
Most of Middle East had large minority of Nestorianism, with state patronage they could become majority in many places. Kurdistan, Levant, and Mesopotamia region could become stronghold of Christianity.
Nestorianism also could become strong minority religions in China, Korea, Manchuria, and Tamir Basin. In Western Steppe (Ukraine) interactions between Greek Church and Nestorian Church would develop, pagan Lithuania and various Rus states could be deeply influenced by Nestorianism.
Nestorian mysticism, interactions with other religions (Buddhism, Taoism, Islam, Manicheanism, Zoroastrianism), and how it interact with Mongol pagan and shamanistic traditions could develop very different Christianity than Western Christianity.