You know we are lucky. If the Germanic invaders hadn't successively converted to Trinitarian Christianity then it's entirely possible that Arianism and Catholic-Orthodoxy would be the two main branches of Christianity today.
Catholic-Orthodoxy would be the Roman branch of Christianity, and Arianism would be the Germanic branch of Christianity. Thank the Lord that Trinitarianism ultimately won out in the end and now all Christians, even the darn Baptists, are Trinitarians and all non-Trinitarian sects are minuscule.
It could have been different though, non-Trinitarians could've been as numerous as Trinitarians.