The forward struck a hat-trick inside the opening 40 minutes in Boston, with Rinsola Babajide also on target in an incredible first half for Vicky Jepson’s team.
Babajide grabbed a fifth goal shortly after the re-start before Sweetman-Kirk netted her fourth with five minutes remaining to cap an impressive showing from the Reds.
LFC Women had kicked off their United States tour with a 2-2 tie against Cleveland Ambassadors in Notre Dame last week, with Sweetman-Kirk’s late strike salvaging a draw.
And the striker picked up where she left off by setting the ball rolling in the seventh minute when she tapped in following sterling play from Babajide to create the opening.