Let me put it like this: "if" a new and common ideology was to arise throughout the Germano-Norse ethno-cultural sphere from between the Fourth-Fifth Centuries, one based on the traditional spiritualism of the Germanic peoples that turned out to prove useful to the rulers of the different tribes, which would keep them all relatively unified against European Christendom and other forces, so that as they spread like they did OTL from Britain to Russia, how would this impact on European and possibly even Central Asian and Middle-Eastern geo-political history?
1) The Danelaw headed by a single dynasty, without falling into occasional infighting, and being overcome by the West Saxons of King Alfred?
2) The Kievan Rus maintaining a unique Norse-Slavic culture, are easily rivalling the Byzantines in military strengh, and launching expeditions as far as the Caspian Sea region?
3) Perhaps the Franks and the Lombards never adopt Catholicism, and the Roman Church in Italy and Gaul becomes marginalized into a political tool for controlling the native Latin population?
4) Would the Byzantines and the early Muslim Caliphates view them as a common enemy?
5) No eastern crusades, as the strategy of Christendom is a defensive one.
6) Unless the Visigoths adopted the new Asa creed of their northern cousins, they'd be wedged between Muslim encroachment, and and that of the Norse.