Bellingham signed for BVB from Birmingham City over the summer, but not before visiting United's Carrington training HQ.
He told BBC Sport: "Manchester United have a great squad - and my decision had nothing to do with Man United. Dortmund was the best place for me.
"After that, you ignore everything else.
"It's been easy to build a connection because I can relate to my team-mates a little bit more. A lot of them are in a similar boat, especially Jesus and Gio, who are a similar age and points in our career."