Swiatek triumphed 6-2, 6-2 in Saturday night's final at Memorial Drive to collect her second career title, following her French Open victory last year.
The 19-year-old's dominant final completed a stellar tournament in which she didn't drop a set - in five matches, she lost just 22 games.
Swiatek seized momentum midway through the first set: leading 3-2, she broke Bencic's serve when the Swiss world No. 12 double-faulted three times.
Swiatek, the world No. 18, held serve and then broke Bencic again to take the first set in 35 minutes.
In the second stanza, Swiatek again crafted a decisive gap midway through by breaking Bencic's serve in the fourth game to create a 3-1 lead.
From there, the daughter of former Polish Olympic rower Tomasz Swiatek, who competed at the 1988 Games in Seoul, had no trouble finishing off Bencic, who has now lost seven of her 11 career finals.
The third-seeded Mathison and Krawczyk triumphed 6-7, 6-4 and 10-3 in the deciding super tiebreak.