The 25-year-old impressed in his first fight since losing all his lightweight titles to George Kambosos Jr last November.
The Australian has since relinquished the WBA, IBF and WBO belts to Devin Haney in June, though a rematch with Lopez is not out of the question.
The American put Campa to the canvas at the start of the seventh round, and quickly followed up with a number of stinging shots as referee Tony Weeks called a stop to the fight.
Speaking after his victory, 17th of his professional career and 13th by stoppage, Lopez said: "I am grateful for this, I have returned. I got to work a little bit more on some things, but overall it was good.
"It's been a while. There was a lot on my mind. I nearly almost died [in] the last fight, so that was weighing on my mind, I had to clear it out."
The lightweight boxer then expressed his desire to fight in the UK. Lopez has a number of possible opponents who he could fight in Britain, including Ryan Garcia, Josh Taylor and Jack Catterall.
"I know I have so much love over there and I just need to be over there and embrace that environment and enjoy the energy because you guys are diehard boxing fans," he added.
"I don't care who it is. It could be Ryan Garcia, Taylor, Catterall, I don't care, I want to be at the O2 Arena."