Injury-hit USA squad makes it to Brazil 2014.
USA goalkeeper Tim Howard made a pair of key saves in the first half to keep the match scoreless before Johnson headed home a Donovan corner just four minutes into the second half.
“In the second half we were fantastic,” Howard said. “We knew we were going to create chances and we did.”
The Americans were missing four key players, including midfielder Michael Bradley who sat out with an ankle injury. Three others were serving suspensions after picking up cautions in last Friday’s defeat to Costa Rica.
Clint Dempsey missed a kick in the dying seconds which could have made it 3-0.
The result stretches the Americans’ unbeaten streak at home in World Cup qualifiers to 26 games, while Mexico has lost two straight in qualification.
The top three CONCACAF nations qualify for next year’s 32-nation event in Brazil. The fourth place finisher will end up in a playoff with New Zealand.
The loss puts Mexico in a precarious position as they face a must-win game against Panama on October 11.
Mexico was playing its first game since coach Chepo de la Torre was replaced by Luis Fernando Tena following Friday’s 2-1 defeat to Honduras at Azteca Stadium.
In the Costa Rica contest, Randall Brenes opened the scoring in the 75th minute to give Costa Rica a 1-0 lead before Jermaine Anderson tied it for Jamaica in stoppage time.
Honduras was on the verge of taking a huge step toward qualification, but Panama equalized in stoppage time when Gabriel Torres scored his second of the contest.