In 5th century Nestorianism was deemed as a heretical Christianity, went into the eastern fringe of Roman Empire/Sassanid Empire, survived for centuries, and then emerged in the 20th century as a nationalist movement.
In late antiquity we have lots of strains in Christianity deemed as heretical. Monophysitism in Syria and Egypt are the other two biggest examples. But why don't we hear similar movement like the Assyrian nationalism? The 20th century Egyptian Coptic derived its legacy from the Egyptian Monophysitism, but I'm not sure if it's a movement akin to Assyrian nationalism?
I think your question has some problematic assumptions: primarily, asserting that Assyrian nationalism is built upon Nestorianism.
The church on the fringe of the Eastern Empire, predominantly operating in the Syrian language, and throughout the Parthian and then Sasanian Empire(s), was functionally, culturally, and linguistically already very separate from the Church throughout the Roman Empire, and that was already a division that had taken place more or less organically long before you get to the Nestorian-controversy of the 5th century. Indeed, the number of Christians in the Chruch of the East probably rivalled that of those in the Roman Empire, so thinking of them as a minor offshoot is generally incorrect.
The identification of the Church of the East (and many variants/branches) with ‘Nestorianism’ does have some minor basis in fact, primarily because Syrian-language churches were unwilling to condemn Nestorius or assent to the Council of Chalcedon 451. But this was not their (self-)defining feature nor their origin, and modern scholars generally abandon the term ‘Nestorian’ when talking about these Eastern churches.
Contemporary Assyrian nationalism is not restricted to one branch of Christianity, indeed crosses denominational boundaries, and although it is generally identified with Christian Assyrians, it is Assyrian nationalism, based on a claim to historical and ethnic continuity from ancient Assyria. But not all members of these churches (I am thinking of the Assyrian Church of the East, Syriac Orthodox Church, Ancient Church of the East, among others) identify as Assyrian or trace their identity to Assyria. Notable, some of the historical lineage of members of these groups would by Syrian and so located in modern Syria and Iraq, whereas the ideology of Assyrian nationalism calls for a nation state in northern Iraq centered on Nineveh in line with ancient Assyria.
My point is, it is not really accurate to suggest that Nestorianism, a particular 5th century theological current, created 19th to 21st century Assyrian nationalism, and so it is even more problematic to ask about similar schisms creating similar nationalism movements. One would have to engage in a much closer study of the history of Eastern churches, ethno-linguistic identity, and the emergence of nationalist movements, to make a persuasive case that Assyrian nationalism is meaningfully indebted to Nestorianism.