Mackenzie, a member of the victorious U.S. Curtis Cup team, ended the two days at 3-under-par 139 moving into match play.
Tiffany Joh and In Kyung Kim each ended the two days at 1-under-par, while Ayaka Kaneko, Mi Jung Hur and Jane Park, the 2004 Women's Amateur champion, all ended at even-par.
Mackenzie, of Yakima, Washington, had three birdies and two bogeys on the Witch Hollow Course at the Pumpkin Ridge Golf Club Tuesday. She will play Leah Wigger of Louisville, Kentucky in the first round of match play Wednesday. The competition concludes with a 36-hole final on Sunday.
Kim looked as if she would take medalist honors, but she double-bogeyed the 17th hole and bogeyed the 18th.
Ashley Knoll and Katharina Schallenberg both ended 36 holes of stroke play at 1-over, while Alison Whitaker, Isabelle Lendl and Lindy Duncan were each at plus-2.
The cut was at 9-over-par 151. Seven golfers played for the final five spots with Wigger, Theresa Paik, Alice Kim, Jenna Pearson and Lara Tennant all advancing.