Latitude isn't everything, the Gulf stream and the Atlantic Meridional Overturning Circulation keeps western Europe much warmer than it otherwise would be just based on it's latitude.
Fun fact that current is weakening somewhat because of climate change so European winters may get much worse. [0]
It's probably both I'm not a climate scientist so I can't really say one is more important than the other but the AMOC does bring warm water up the coast as well and if that goes away and the water cools the air brought over by the Gulf Stream will probably be colder as well.
Fun fact that current is weakening somewhat because of climate change so European winters may get much worse. [0]
[0] https://www.smithsonianmag.com/smart-news/ocean-current-keep...