Verstappen, who is expected to win his second title this weekend, was some eight tenths in arrears as Leclerc took a visit to the gravel in his Ferrari to lap only 10th fastest.
With the 3.6-mile circuit still sodden, no one ventured out initially for the 90-minute session - FP2 having been extended by half an hour to theoretically accommodate a Pirelli test run.
But with the mule tyre a slick compound, the extra runtime was effectively meaningless in the lasting wet, although FP2 at Austin will similarly be extended to feature another shakedown.
Nicholas Latifi was eventually the first driver to hit the track after five minutes, touring on a set of full wets for two laps until he took to the Turn 16 escape road with a temporary car issue before spinning and resuming. He was joined by Carlos Sainz and Daniel Ricciardo.
After 12 minutes, Sainz became the first runner to set anything like a representative time as the Ferrari driver dropped below 1m50s to post a 1m49.615s. By comparison, Fernando Alonso set the pace in FP1 courtesy of his 1m42.248s run to find three tenths over Sainz.
