Nathan Dyer had put Swansea ahead with a 57th-minute strike - the first goal to be scored in the debut football match at Miller Park, the home of the Milwaukee Brewers baseball team - before Hernandez equalised in the last seconds of the game.
Jazz Richards was adjudged to have fouled an opposing player in the box, with goalkeeper Gerhard Tremmel unable to keep out the Chivas substitute from the spot.
Both sides ended the game with 10 men after referee Andres Pfefferkorn dismissed Neil Taylor and Chivas' Jesus Sanchez with 10 minutes remaining after they squared up to each other following a challenge.
After a goalless first half which saw Jonjo Shelvey strike the crossbar with a thunderous free-kick and Wayne Routledge's effort ruled offside, Swans boss Garry Monk made 10 changes, with Dyer opening the scoring soon after the break.
Swansea striker Rory Donnelly had a header denied at the back post before Tremmel stopped a shot by Omar Esparza and Hernandez narrowly missed with a free-kick.
Taylor and Sanchez were then both dismissed before the late penalty award saw the match finish all square.
- Sports & Recreation
- Gerhard Tremmel
- Nathan Dyer
- Milwaukee Brewers
- Jesus Sanchez