The Australian is one of the title favourites after his run to the Wimbledon final and strong form on the North American hard courts, and he admitted he is putting a lot of pressure on himself after battling to a 7-6 (3) 6-4 4-6 6-4 victory.
"I wasn't going out there expecting him to not be good or something," Kyrgios said of the Frenchman. "But his level was really, really good. I was really fortunate to get through in four sets. I was down 4-4 0-40 in the fourth, I played some really low-percentage tennis to get out of that game.
"It was one of those matches where you kind of survive. I am relatively happy with my form. It's so stressful now because, every match I play, I'm expecting to play so good.
"I've got to probably lower the expectation of expecting to play like a Wimbledon final every time. I almost don't know who I am any more, to be honest, because that's not me.
"I feel like I'm really professional right now. I never thought that the Wimbledon final would make me that way. I thought it would be the other way, the reverse, almost a bit lax and a bit chilled with it."
The warning came after Kyrgios dropped serve late in the second set, with the Australian berating his support camp.
On his marijuana complaints, meanwhile, which led the umpire to remind the crowd not to smoke, Kyrgios said: "I'm a heavy asthmatic. When I'm running side to side, I'm struggling to breathe, probably not something I want to be breathing in in between points."
The Australian next faces unseeded American JJ Wolf.
World number one Daniil Medvedev was given the late shift on Arthur Ashe Stadium after the Serena Williams show but avoided any drama against Frenchman Arthur Rinderknech, coming through 6-2 7-5 6-3 to set up a clash with Wu Yibing, who became the first Chinese player to reach the third round at the US Open.