The USA captain left Dortmund last summer for the Blues.
"The Dortmund fans are the most passionate I have ever seen in my life," Pulisic told ESPN.
However, he says playing in England is something else.
"I was most struck by the football culture. Throughout the country, football means a lot to people. I think that's the biggest difference I've noticed so far."
Pulisic is currently working his way back from injury.
"In the coming weeks, I will do everything to be there again soon," he added.