Allie Knight fired a bogey-free 69 while Sandra Changkija produced another 40-foot birdie finish at 18 as the Americans tightened their grip.
The USA seized control at Carden Park as Stephanie Connelly Eiswerth shared the individual lead and two team-mates broke par.
The unbeaten USA team heads to Carden Park for the Women’s PGA Cup 2026, facing its first overseas test from 3-5 September in England.