Why does Northwestern Europe have a milder climate when compared to regions at the same latitude?

There has been a great deal of study as to why the northwestern regions of Europe have a warmer climate than regions elsewhere at similar latitudes. It has been thought for many years that the Atlantic Gulf Stream led to warmer temperatures in northwestern Europe because the warm waters from near the Equator, flowing toward northwest Europe, led to milder air and milder temperatures there. However, recent research indicates that the Gulf Stream actually draws colder air from the polar regions into regions just west of this warmer air. As a result, areas along the East Coast of the United States and Canada experience colder temperatures than places at similar latitudes in northwestern Europe. Something similar happens in the Pacific Ocean, leading to warmer temperatures in the western coastal regions of the United States and Canada and colder temperatures at similar latitudes along the east coast of Asia.
https://www.livescience.com/13573-east-coast-colder-europe-west-coast.html