Gareth Taylor's side made it eight wins in a row, as they closed the gap on league leaders Chelsea to two points with a dominant display at St. George's Park.
And the American international was on hand to fire home our second, reacting quickest to volley home after Ellen White’s initial effort had been cleared off the line following a 52nd minute corner.
Lauren Hemp then added a third moments later when her inviting ball to the back post evaded everyone before nestling into the far corner, before Caroline Weir poked home a fourth just after the hour to put the tie to bed.
Substitute Rose Lavelle could have made it five in stoppage time, but the SheBelieves Cup's player of the tournament saw her stinging effort crash against the bar.
Match report: Birmingham 0-4 City
You can watch exclusive CityTV productions with a CITY+ subscription.