Spaniard Fernando Verdasco came through his opening round at the US Men's Clay Court Championship as two seeds fell.
Verdasco proved too good for Carlos Berlocq in a 6-4 6-3 victory on the clay courts in Houston on Tuesday.
The 2014 champion had to recover from being 3-1 down in both sets to secure his win.
Querrey, runner-up last year, served eight aces in his 6-4 7-6 (7-4) win over teenage lucky loser Reilly Opelka.
However, two seeds made way.
Steve Johnson went down to fellow American Donald Young 6-4 6-3 and Paolo Lorenzi was beaten by Tommy Paul 6-2 6-3.
Cypriot seventh seed Marcos Baghdatis needed just 49 minutes to get beyond the first round, thrashing Diego Schwartzman 6-0 6-0.
Wildcard Tim Smyczek battled through with a 4-6 7-6 (7-5) 6-4 win over Nicolas Kicker and Matthew Barton overcame Frances Tiafoe 6-3 6-4.
Lukas Lacko also progressed, beating Dmitry Tursunov 6-1 7-5, and Benjamin Becker overcame German countryman Michael Berrer 7-6 (8-6) 6-0.