CoCo Vandeweghe will next face French sixth seed Carolina Garcia.
Venus Williams' win came in her 1,000th career match and her 22nd singles appearance in a tournament she first played in 1999.
The United States duo of Shelby Rogers and CoCo Vandeweghe beat Belarusian duo Aryna Sabalenka and Aliaksandra Sasnovich to clinch Fed Cup crown for the 18th time.
CoCo Vandeweghe, this season's Australian Open and US Open semi-finalist, ranked 10th in the world, fired 12 aces to win the match against Aryna Sabalenka of Belarus.
CoCo Vandeweghe won her Fed Cup match 6-4, 6-4, in one hour 27 minutes her first ever meeting with the 23-year-old Aliaksandra Sasnovich.
The United States Fed Cup team is made up of world number 10 CoCo Vandeweghe, US Open champion Sloane Stephens, Shelby Rogers and Alison Riske.
Venus Williams, a seven-time major champion, was seeking her first grand slam title since 2008
Venus Williams was imperious in banishing her power-hitting fellow American 6-7 (3/7), 6-2, 6-3 on Rod Laver Arena, striking a blow for the tennis old guard.
Coco Vandeweghe, who had knocked out top seed Angelique Kerber in the fourth round, defeated Garbine Muguruza 6-4, 6-0 to reach the Australian Open semis
While Sania Mirza and Rohan Bopanna advanced in the 2016 US Open, Leander Paes failed to progress past the second round in the mixed doubles event