Pulisic capped his performance off with a well-taken goal to add to Kai Havertz's opener in the 2-0 win.
"It's a great start for us," Pulisic commented post-match. "We knew we needed to get a good result in this first leg.
"I thought we defended really well throughout the game and we took our chances at the other end when we needed to.
"Obviously there's still a lot of work to do, it's only half-time in the tie, but we are really happy with our work so far and with the lead we can take with us to Lille.
"We know it will be a difficult game over there though. They are a dangerous team, with a lot of speed up front so we need to be careful of them on the counter-attack for sure.
"But I'm sure if we put in another good performance like this one then we can come away with the victory again."
N'Golo Kante laid on the pass for Pulisic's goal.
The USA captain went on: "Kante is amazing.
"The way he drives with the ball is incredible and I knew he'd find me with the pass, so it was just a case of me staying up there with him and getting into the right area in the final third.
"I was able to do that, N'Golo made the perfect pass and thankfully I had just enough room to touch it to the side and then pass it past the goalkeeper. So I'm really happy to have scored and to have helped the team get a good victory."