The third seed quickly found his range on Arthur Ashe Stadium to earn his 50th tour-level win of the season after a match that lasted for one hour and 16 minutes.
The fifth seed overcame an aggressive display from the 21-year-old Nava, who smashed 72 winners to Ruud's 27 but lacked the consistency needed to pull off an upset.
Reigning US Open winner and World No.1 Carlos Alcaraz will start his title defence against Dominik Koepfer and could meet sixth seed Jannik Sinner in the quarterfinals.
The World No.1 Iga Swiatek and defending champion Jessica Pegula headline the entry list for the Guadalajara Open, a WTA 1000 tournament that begins on September 17.