Geographical Determinism is always a contentious topic, but in this specific case, it's worth noting that Charlemagne's campaigns against the Saxons only reached the Elbe until 802, having previously concentrated largely on establishing control over Italy, and pushing the frontier Eastwards into Carinthia and Pannonia. His Merovingian predecessors had been mostly concerned politically with expanding their political control from their Austrasian heartlands over what we today consider 'France'. What this means in practice is that there is no Christian frontier with Scandinavia until, essentially, the ninth century.

In contrast, the English had been well established in the British Isles for around some three centuries at this point. Æthelberht of Kent, the first Christian English king, had a close political and economic relationship with his neighbour, the Merovingian king Charibert I, having married his daughter Aldeberge around 580. Aldeberge was a Christian and brought her own priests to Kent, although her husband resisted attempts at conversion until the Augustinian mission of 597, likely for political reasons. The conversion of England was a sporadic process that took around a century to complete, but by the time that the Carolingian frontier reached Scandinavia, much of England had been Christian for at least a century.